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THE  HEMOLYMPH  NODES 
OF  THE  SHEEP 

STUDIES  ON  HEMOLYMPH  NODES  I. 


A.  W.  MEYER 

FROM  THE 

DIVISION  OF  ANATOMY 

DEPARTMENT  OF  MEDICINE 

STANFORD  UNIVERSITY 


STANFORD  UNIVERSITY,  CALIFORNIA 

PUBLISHED  BY  THE  UNIVERSITY 

1914 


UNIVERSITY  SERIES 

INHERITANCE  IN  SILKWORMS,  I.  Vernon  Lyman  Kellogg,  Professor 
of  Entomology.  89  pp.,  4  plates.  1908.  Price  $1.00. 

THE  OPISTHOBRANCHIATE  MOLLUSCA  OF  THE  BRANNER-AGASSIZ  EXPE- 
DITION TO  BRAZIL.  Frank  Mace  McFarland,  Professor  of  His- 
tology. 105  pp.,  19  plates.  1909.  Price,  $1.00. 

A  STUDY  OF  THE  NORMAL  CONSTITUENTS  OF  THE  POTABLE  WATER  OF 
THE  SAN  FRANCISCO  PENINSULA.  John  Pearce  Mitchell,  Assis- 
tant Professor  of  Chemistry.  70  pp.,  I  map.  1910.  Price,  500. 

SYNOPSIS  OF  THE  TRUE  CRABS  (BRACHYURA)  OF  MONTEREY  BAY,  CALI- 
FORNIA. Frank  Walter  Weymouth.  64  pp.,  14  plates.  1910. 
Price,  SQC. 

THE  OSTEOLOGY  OF  CERTAIN  SCOMBROID  FISHES.  Edwin  Chapin  Starks, 
Assistant  Professor  of  Zoology.  49  pp.,  2  plates,  I  text  figure. 

1911.  Price,  500. 

A  PHYSICAL  THEORY  OF  ELECTRIFICATION.  Fernando  Sanford,  Profes- 
sor of  Physics.  69  pp.,  2  plates.  1911.  Price,  5Oc. 

THE  MATZKE  MEMORIAL  VOLUME.  Papers  by  John  Ernst  Matzke,  late 
Professor  of  Romanic  Languages,  and  Thirteen  Colleagues.  162 
pp.  1911.  Price,  $1.00, 

DAS  HISTORISCHE  PRASENS  IN  DER  ALTEREN  DEUTSCHEN  SPRACHE.  Bruno 
Boezinger,  Assistant  Professor  of  Germanic  Languages.  91  pp. 

1912.  Price,  5oc. 

THE  EFFECT  OF  A  STRICTLY  VEGETABLE  DIET  ON  THE  SPONTANEOUS 
ACTIVITY,  THE  RATE  OF  GROWTH,  AND  THE  LONGEVITY  OF  THE 
ALBINO  RAT.  James  Rollin  Slonaker,  Assistant  Professor  of 
Physiology.  36  pp.,  I  plate,  15  text  figures.  1912.  Price,  500. 

CATALOGUE  DE  Tous  LES  LIVRES  DE  FEU  M.  CHAPELAIN.  (Bibliotheque 
Nationale,  Fonds  Franqais,  Nouv.  Acq.,  No.  318.)  Colbert 
Searles,  Associate  Professor  of  Romanic  Languages.  119  pp.,  2 
plates.  1912.  Price,  75c. 

THE  DUDLEY  MEMORIAL  VOLUME.  Papers  by  William  Russel  Dudley, 
late  Professor  of  Botany,  and  Several  Colleagues.  137  pp.,  12 
text  figures,  9  plates.  1913.  Price,  $1.00. 

THE  FISHES  OF  THE  STANFORD  EXPEDITION  TO  BRAZIL.  Edwin  Chapin 
Starks,  Assistant  Professor  of  Zoology.  77  pp.,  15  plates.  1913. 
Price,  75c. 

(Continued  on  third  page  of  cover.) 


IJBRARI 

OF  CAUFORWA 

RWliRSlDE 


LELAND  STANFORD  JUNIOR  UNIVERSITY  PUBLICATIONS 
UNIVERSITY  SERIES 


THE  HEMOLYMPH  NODES 
OF  THE  SHEEP 

STUDIES  ON  HEMOLYMPH  NODES  I. 


A.  W.  MEYER 

FROM  THE 

DIVISION  OF  ANATOMY 

DEPARTMENT  OF  MEDICINE 

STANFORD  UNIVERSITY 


STANFORD  UNIVERSITY,  CALIFORNIA 

PUBLISHED  BY  THE  UNIVERSITY 

1914 


STANFORD   UNIVERSITY 
PRESS 


HEMOLYMPH   NODES  OF  THE  SHEEP 
STUDIES  ON  HEMOLYMPH  NODES,  I 


CONTENTS. 

Distribution,  occurrence  and  appearance. 

Lymphatic  and  vascular  relations. 

The  microscopic  structure. 

The  cellular  content. 

The  question  of  mixed  nodes. 

The  genesis  of  intermediate  forms. 

Classification. 

Functions. 

References. 


INTRODUCTION 

Although  a  number  of  species  were  investigated,  this  paper  has  pur- 
posely been  limited  to  the  sheep  (Ovis  aries),  in  order  that  a  more  com- 
prehensive review  of  large  numbers  of  hemolymph  nodes  could  first  be 
made.  For  even  a  slight  familiarity  with  the  subject  makes  it  evident 
that  it  is  not  only  necessary  to  examine  many  nodes  in  the  different 
regions  of  the  same  animal,  but  also  to  examine  large  numbers  in  different 
animals,  and  perhaps  of  animals  of  varying  ages  as  well.  Moreover,  a  very 
comprehensive  comparative  study,  although  probably  indispensable  for 
the  elucidation  of  some  of  the  intricate  problems  of  structure,  function 
and  development,  usually  introduces  many  additional  and  related  prob- 
lems which  tend  to  obscure  the  issue  regarding  a  single  species.  By 
first  subjecting  one  species  to  a  thorough  examination  the  problem  can 
also  be  better  defined,  many  conflicting  statements  can  be  ignored,  and 
much  confusion  avoided.  It  also  seemed  probable  that  an  initial  and 
careful  comprehensive  examination  of  one  species  would  make  it  possible 
to  decide  with  some  degree  of  certainty  whether,  as  recently  and  so  often 
before  reiterated,  these  organs  in  a  given  species  are  true  hemolymph 
nodes  or  not,  and  whether  a  transformation  of  hemolypmh  nodes  into 
hemal  or  lymphatic  nodes  takes  place.  To  this,  and  to  some  other  ques- 


4  HEMOLYMPH    NODES    OF    THE    SHEEP 

tions,  an  unusually  large  collection  of  material  and  a  series  of  observa- 
tions of  some  magnitude  seem  to  justify  a  definite,  even  if  not  a  final  or 
necessarily  a  conclusive  answer. 

Although  there  are  many  considerations  which  would  seem  to 
suggest  that  the  term  hemolymph  is  a  misnomer  when  applied  to 
these  nodes,  this  designation,  which  was  suggested  by  Russel  and 
first  used  by  Robertson  [24],  is  retained  throughout  a  part  of  this 
article  in  order  not  to  introduce  a  discussion  of  terms  at  the  very 
beginning.  It  is  necessary  to  state,  however,  that  the  terms  periph- 
eral and  central  sinuses  have  been  rejected  altogether,  because  no  one 
has  shown  that  they  are  comparable  to  the  corresponding  structures  of 
lymph  nodes.  The  only  true  sinuses  of  hemolymph  nodes  are  the  radicles 
of  the  venous  system ;  the  venous  lacunae  of  Weidenreich ;  which  struc- 
turally are  tremendously  dilated  capillaries,  and  which  form  an  integral 
part  of  the  vascular  system  of  the  hemolymph  node.  The  so-called  per- 
ipheral and  central  sinuses  of  the  hemolymph  nodes  can  much  more 
properly  be  designated  as  subcapsular  or  marginal  and  central — in  the 
sense  of  internal  only — blood  spaces  or  areas,  than  as  sinuses,  since  they 
are  neither  in  direct  communication  with  either  the  lymphatic  or  vas- 
cular circulations,  as  a  rule. 

The  sheep  was  also  chosen  as  the  first  subject  of  experiment  and 
inquiry,  because  almost  all  investigators  of  hemolymph  nodes  had  studied 
them  in  this  animal  to  a  greater  or  less  extent;  because  the  nodes  are 
much  more  numerous  than  in  any  of  the  other  domestic  animals 
studied;  and  since  a  convenient,  inexpensive,  and  also  an  abundant 
supply  of  material  was  afforded  by  the  abattoirs,  where  an  unlimited 
number  of  embryos  and  foetuses  of  all  ages  could  easily  be  obtained.  In 
addition,  however,  the  carcasses  of  several  dozen  new-born  lambs,  two 
lambs  of  about  five  weeks  old,  and  two  young  sheep  six  to  eight  months 
old,  received  special  scrutiny.  Besides,  several  thousand  carcasses  were 
examined  and  many  thousands  inspected  in  the  abattoirs  in  various  parts 
of  the  country.  This  varied  material  naturally  afforded  an  excellent 
opportunity  for  observations  regarding  the  relation  of  sex,  age,  breed, 
pregnancy,  states  of  health  and  nutrition,  castration,  locality,  seasonal 
changes,  and  hygienic  conditions  in  general,  to  the  occurrence,  size,  num- 
ber and  position  of  these  "enigmatical  structures."  Living  sheep  could 
also  be  subjected  to  close  scrutiny,  the  carcasses  inspected  later,  and  a 
thorough  examination  made  of  the  viscera,  with  a  view  to  detecting  any 
possible  compensatory  relationship  between  hemolymph  nodes  and  other 
organs,  in  varying  conditions  of  nutrition  and  of  health. 


DISTRIBUTION,    OCCURRENCE   AND    APPEARANCE  5 

DISTRIBUTION,  OCCURRENCE  AND  APPEARANCE 

Even  a  cursory  inspection  of  hundreds  of  carcasses  in  the  large  abat- 
toirs confirmed  the  statement  that  the  lumbar  subvertebral  region  is  the 
place  in  which  the  hemolymph  nodes  of  the  sheep  are  by  far  the  most 
numerous,  and  that  their  occurrence  near  the  renal  arteries  has  been 
over-emphasized.  Since  the  lumbar  region  is  especially  accessible,  these 
nodes  were  chosen  as  the  object  of  special  study.  In  all  except  very  fat 
sheep  they  lie  exposed  to  view,  and  can  always  be  recognized  as  a  whole, 
even  if  not  individually,  as  hemolymph  nodes  by  the  unaided  eye.  Hard- 
ening the  tissue  containing  them  in  formaline,  as  stated  by  Warthin  [31!, 
did  not,  in  my  experience,  make  them  any  more  conspicuous.  Moreover, 
since  their  conspicuousness  in  the  fresh  state  is  due  to  the  contained 
blood,  any  fixing  or  hardening  agent  which  does  not  increase  the  color 
contrast  between  fresh  blood  and  the  fat  in  which  they  lie  can,  in  the 
nature  of  things,  not  make  them  more  conspicuous  except  in  so  far  as 
shrinkage  of  the  surrounding  tissues  makes  them  more  prominent. 
Neither  did  formaline  help  materially  in  distinguishing  very  small  nodes 
from  punctiform  hemorrhages,  since  it  affected  both  alike,  even  if  not  to 
a  like  degree. 

Even  if  they  be  small,  a  reasonably  accurate  count  of  the  hemolymph 
nodes  can,  however,  be  made  without  difficulty  in  most  cases  in  the  fresh 
state.  From  careful  counts  in  several  dozen  carcasses,  supplemented  by 
inspection  of  several  thousand  more,  it  was  found  that  in  sheep  of  mixed 
breeds  the  number  of  nodes  in  the  lumbar  sub-vertebral  region  varied 
from  a  few  to  at  most  fifty  or  sixty  nodes.  Although,  to  be  sure,  averages 
can  mean  little  because  of  the  great  fluctuations  which  exist,  a  fair  aver- 
age number  in  this  region  in  young  sheep,  according  to  my  observations, 
would  be  twenty  to  thirty  nodes.  The  total  number  in  the  whole  animal 
varied,  however,  from  half  a  dozen  to  a  hundred  and  fifty  nodes  in  ex- 
ceptional cases.  Three  or  four  hundred  nodes  of  macroscopic  size,  as 
estimated  by  Robertson  [24]  and  confirmed  later  by  Warthin  [34]  as  an 
average  number,  were  never  found,  in  the  entire  body,  including  the 
viscera,  even  in  the  most  exceptional  cases.  It  is  possible,  to  be  sure, 
that  there  are  breeds  or  conditions  which  justify  the  above  estimates; 
but  all  evidence  obtained  in  mixed  breeds  of  Merino,  Shropshire  and 
Southdown— and  just  sheep— in  the  East,  in  the  Middle  States,  and  in 
the  West,  makes  this  supposition  very  improbable. 

In  foetuses  near  term,  in  several  dozen  new-born  and  in  four  lambs 
four  weeks  to  six  months  old,  for  example,  in  which  a  careful  examina- 
tion of  the  fat  in  all  regions  was  made  with  the  aid  of  a  hand  lens,  a 


6  HEMOLYMPH    NODES    OF    THE    SHEEP 

dozen  to  a  few  dozen  nodes  at  most  were  found.  In  the  new-born  only 
from  four  to  six  may  be  present.  From  the  examination  of  a  large  num- 
ber of  foetuses  the  statement  that  the  younger  the  foetus  the  fewer  the 
nodes  that  can  be  recognized  as  hemolymph  nodes,  seems  justified;  for 
it  is  difficult  indeed,  as  a  rule,  to  successfully  identify  macroscopically  any 
nodes  as  hemolymph  nodes  in  any  region,  in  foetuses  less  than  three  to 
four  months  old.  Nevertheless,  a  striking  fact  is  the  occurrence  of  a 
greater  number  of  hemolymph  nodes  in  lambs  and  young  sheep.  In  abat- 
toirs, in  which  occasionally  almost  a  thousand  sheep  are  slaughtered 
daily,  it  is  quite  possible,  in  spite  of  customary  mechanical  osteological 
conversions  of  mutton  into  lamb,  to  determine — not  in  individual  cases, 
of  course — whether  lambs  or  sheep  are  being  slaughtered,  by  a  cursory 
inspection  of  a  number  of  nodes  present  in  the  lumbar  region  alone. 
Moreover,  such  a  differentiation  is  especially  easy  when  lambs  and  sheep 
have  been  put  into  separate  pens  before  slaughtering,  thus  avoiding  a 
mixing  of  the  individual  carcasses.  In  fact,  these  differences  are  suf- 
ficiently marked,  so  that  even  the  butchers  are  aware  of  it  and  not  infre- 
quently comment  upon  the  fact.  In  one  instance,  for  example,  in  which 
a  lot  of  six  thousand  wethers  were  slaughtered  on  successive  days,  two 
of  the  butchers  spoke  of  the  smaller  number  of  nodes  found  in  "Western" 
sheep,  adding  that  in  the  home  or  "Eastern"  sheep  more  were  to  be 
found.  Their  observations  were  entirely  correct,  but  their  conclusions 
were  faulty,  for  it  was  incorrect  to  infer  that  locality  or  castration  were 
the  causative  factors  in  this  difference,  v  Schumacher  [27]  also  men- 
tions the  fact  that  they  are  more  common  in  young  sheep.  As  reported 
by  Weidenreich  [37]  and  Warthin  [31],  the  belief  of  butchers  that  sheep 
fresh  from  pasture  have  more  hemolymph  nodes,  also  found  confirma- 
tion ;  but  this  is  likely  explained  by  the  fact  that  such  animals  are  usually 
lambs,  or  largely  lambs  or  young  sheep,  rather  than  by  the  state  of  nutri- 
tion of  the  animals ;  for  such  an  influence  of  diet  would  be  as  remarkable 
as  surprising  and  unlikely. 

No  definite  grouping  of  the  hemolymph  nodes  of  the  sheep  was 
found  to  exist,  although  they  occur  more  abundantly  in  fairly  well-defined 
regions.  Besides,  in  the  lumbar  sub-  and  para-vertebral  regions  they 
commonly  occur  in  numbers  in  the  para-rectal  fat;  more  rarely  near 
the  renal  vessels ;  and  sometimes  in  a  more  or  less  complete  series  extra- 
pleurally  in  the  intercostal  spaces  immediately  lateral  to  the  vertebral 
column  and  near  the  origins  of  the  great  vessels,  in  close  proximity  to 
the  lymph  nodes  between  the  cervical  and  thoracic  portions  of  the  thymus, 
and  in  the  region  of  the  head  thymus  adjacent  to  the  para-thymus  glands. 


DISTRIBUTION,    OCCURRENCE    AND    APPEARANCE  7 

From  the  latter  glands  they  are  indistinguishable  in  the  fresh  state,  as 
pointed  out  by  Drummond  [5]  and  as  previously  reported  by  the  writer. 
They  never  were  found  on  the  diaphragm  as  reported  by  Warthin  [34], 
on  the  parietes,  or  in  the  sub-scapular,  axillary  or  inguinal  regions  as 
reported  by  Meek  [17]  in  pathological  conditions  in  man,  and  but  seldom 
and  only  in  very  small  numbers  in  the  omentum  and  in  the  mesentery. 
The  latter  fact  is  in  marked  contrast  to  the  occurrence  of  supernumerary 
spleens  in  the  cat  (Felis  domestica}  and  dog  (Cants  familiaris)  as  re- 
ported elsewhere.*  Those  found  in  the  thoracic  cavity,  in  the  cervical 
region,  and  especially  in  the  intercostal  spaces,  were  smaller,  more 
spherical,  and  less  prominent  than  those  in  the  lumbar  region.  More- 
over, large  specimens  were  seldom  found  in  any  of  these  regions,  the 
grouping  was  less  distinct,  and  their  presence  less  constant.  The  occa- 
sional intercostal  hemolymph  nodes  not  infrequently  simulated  small  sub- 
pleural  hemorrhages  so  closely  that  they  could  not  be  distinguished  from 
them  in  the  fresh  state,  by  inspection  alone,  and  they  were  too  small  and 
too  flat  for  puncture  injections. 

In  the  cervical  region  their  occurrence  is  far  less  constant  than 
in  the  abdominal  and  thoracic  regions ;  but  they  may  lie  anywhere  be- 
tween the  thorax  and  the  base  of  the  skull.  Usually  one  or  even  several 
nodes  can  be  found,  however,  near  the  bifurcation  of  the  carotid 
arteries ;  and  it  is  not  improbable  that  they  have  been  mistaken  for  and 
described  as  para-thyroid  glands.  In  this  and  in  other  regions  they  often 
lie  so  close  to  the  blood  vessels  that  Weidenreich's  [37]  conclusion  that 
they  never  lie  in  direct  contact  with,  even  if  in  close  proximity  to  them, 
is  not  confirmed;  nor  can  I  confirm  v  Schumacher's  observations  that 
they  usually  lie  near  large  lymph  vessels,  except  in  so  far  as  large  lymph 
vessels  are  present  in  the  lumbar  region.  It  should  be  added,  however, 
that  identification  of  these  small  cervical  nodes  was  not  always  made  by 
means  of  injections,  but  by  microscopic  examination  and  from  gross  ap- 
pearances. Since,  contrary  to  the  statement  of  White  [39],  the  latter 
means  of  identification  is  not  wholly  reliable,  the  above  conclusions  are 
open  to  question  as  far  as  the  occurrence  of  nodes  in  the  cervical  region 
is  concerned.  < 

No  correlation  between  the  size  and  the  number  of  hemolymph 
nodes  in  one  region  with  those  in  another  region,  or  with  the  size,  num- 
ber and  condition  of  the  lymphatic  nodes,  or  with  any  other  condition, 
could  be  established.  Neither  were  they  found  enlarged  in  cases  of  pneu- 
monia, deep  jaundice,  tuberculosis,  or  severe  infections  with  Oesophag- 

*See  appendix,  V. 


8  HEMOLYMPH    NODES    OF    THE    SHEEP 

ostoma  columbanum  or  streptococci.  Pregnancy  or  castration  in  them- 
selves seemed  to  have  no  effect  upon  them.  The  same  is  true  of  differ- 
ences in  sex,  breed,  variations  in  fatness  or  poor  nutrition,  the  locality 
from  which  the  sheep  were  obtained,  or  recent  hygienic  conditions  under 
which  they  were  kept.  These  conclusions  confirm  Weidenreich's  [37] 
observations  in  these  respects.  To  be  sure,  the  implication  is  not  that 
they  are  never  or  can  never  be  affected  by  all  or  any  of  these  things.  In 
case  of  the  human  hemolymph  nodes,  for  example,  it  will  be  recalled  that 
Warthin  [33]  reported  a  definite  relationship  between  the  occurrence  of 
hemolymph  nodes  and  certain  blood  diseases,  and  that  Meek  [17]  also 
found  them  present  in  various  pathological  conditions  in  man. 

While  the  above  statement  gives  the  usual  distribution,  individual 
nodes  may,  however,  occur  anywhere  in  the  fat  near  the  viscera,  from 
the  base  of  the  skull  to  the  coccyx.  Although  no  thorough  examination 
was  made,  none  were  ever  seen  between  the  muscles  of  the  ex- 
tremities, as  stated  by  Crescenzi,*  for  bovines.  No  node  ivas  found 
to  be  constant  in  position,  in  size,  or  in  occurrence.  The  only  con- 
stant characteristic,  aside  from  questions  of  structure  and  function,  is 
their  remarkable  variability,  and  their  constant  occurrence  in  fat.  It  is 
more  than  likely,  however,  that  the  latter  fact  is  without  special  signific- 
ance; and,  as  in  the  case  of  the  lymphatic  nodes,  it  is  probable  that  this 
association  between  hemolymph  nodes  and  fat  has  been  entirely  over- 
emphasized, or  misinterpreted  even,  for  the  regions  in  which  hemolymph 
nodes  occur  are  those  in  which  fat  is  normally  present  in  all  animals. 
Besides,  a  similar  association  exists  between  the  main  vascular,  lymphatic 
and  nerve  trunks,  sympathetic  ganglia,  and  lymphatic  nodes,  the  kidneys, 
accessory  spleens,  etc.  Besides,  many  of  the  pevertebral  nodes  are  not 
imbedded  in  fat  but  can  be  moved  with  the  overlying  peritoneum. 

The  variations  in  the  size  of  hemolymph  nodes  were  as  great  as 
those  in  number,  the  extremes  lying  between  those  invisible  to  the  un- 
aided eye  and  rarely  large  oval  nodes  one  or  two  centimeters  long.  Both 
the  largest  and  the  smallest  nodes  were  found  more  frequently  in  the 
lumbar  region,  but  it  must  be  remembered  that  this  region  was  examined 
much  more  carefully  and  extensively  than  any  other.  In  the  cervical  and 
thoracic  regions  they  were  often  quite  spherical,  and  only  from  two  to 
four  millimeters  in  diameter.  The  smallest  nodes  were  always  more 
globular,  and,  as  already  stated,  often  simulated  punctiform  hemor- 
rhages very  closely.  The  larger  ones,  on  the  other  hand,  were  generally 

*Crescenzi,  L. :  Contribute  allo  studio  dei  gangli  ematici  nei  ruminanti.  La 
Clinica  Veterinaria.  Anno  29,  1906. 


DISTRIBUTION,    OCCURRENCE    AND   APPEARANCE  9 

flattened  on  the  sides  sustaining  the  greatest  pressure,  and  resembled 
lymph  nodes  somewhat  more  closely  in  shape.  Occasionally  a  group  of 
nodes,  or  a  single  node,  was  found,  which  looked  like  a  mass  of  beaded 
blood  vessels,  the  contiguous  walls  of  which  had  fused.  In  other  cases 
isolated  nodes  were  found  from  which  a  beaded  vessel  or  vessels  (figs, 
i  and  2)  closely  simulating  a  lymphatic  vessel  in  form,  but  dilated  with 
blood,  could  be  seen  plainly  for  some  distance  from  the  node,  as  noted  by 
Weidenreich.  In  still  other  instances  the  appearance  was  that  of  a  blood 
vessel  of  somewhat  varying  calibre,  which  formed  a  loop  with  local  thick- 
enings. Pressure  upon  these  nodular  areas  of  the  vessels  would  easily 
bring  about  complete  collapse  in  the  area  of  pressure,  followed  by  sub- 
sequent refilling  with  blood.  This  effect  is  in  marked  contrast  to  the  re- 
sults of  pressure  upon  hemolymph  nodes  of  any  size  and  location,  for 
these  could  never  be  reduced  appreciably  in  size  even  if  subjected  to 
strong  pressure.  Instead  of  collapsing  they  would  invariably  burst.  In 
some  cases  these  nodular  complexes  were  formed  by  a  number  of  small 
nodes  which  lay  in  close  proximity  to  each  other,  or  had  become  more 
or  less  completely  fused.  (Figs.  3  and  4.)  Further  reference  will  be 
made  to  these  later. 

Since  the  descriptions  of  the  external  appearance  of  hemolymph 
nodes  found  in  the  literature  on  the  subject  are  quite  adequate,  this  mat- 
ter will  be  discussed  here  only  in  a  purely  incidental  way.  Intra  vitam 
and  not  long  post-mortem  hemolymph  nodes  usually  have  the  dark 
color  of  moderately  venous  blood.  Rarely,  however,  light  cherry  red 
and  scarlet  nodes  are  seen.  These  are  generally  small,  and  lie  immediate- 
ly beneath  the  peritoneum.  The  prevailing  color  in  fresh  carcasses,  how- 
ever, varied  from  a  bright  red  to  dark  chocolate,  or  even  dull  black.  As 
pointed  out  by  Robertson  [24],  this  variation  is  probably  chiefly  due  to 
differences  in  the  degree  of  post-mortem  oxygenation  of  the  blood  within 
the  node.  That  this  assumption  is  correct  was  shown  by  the  fact  that 
dark-colored  nodes  quickly  turned  to  a  bright  red  color  when  exposed  to 
the  air,  provided  of  course  that  access  to  them  was  not  made  too  difficult 
by  the  presence  of  a  thick  overlying  layer  of  fat,  or  by  the  drying  of  the 
overlying  peritoneum  and  capsule.  This  change  to  a  bright  color  upon 
exposure  is  greatly  accelerated  by  stripping  the  peritoneum  overlying 
the  node,  or,  still  better,  by  exposing  the  node  to  pure  oxygen.  That 
this  color  change  progresses  gradually  from  the  exterior  to  the  interior 
can  also  be  shown  by  sectioning  nodes  which  have  been  exposed  to  the 
air  or  oxygen  for  varying  intervals  of  time.  Such  sections  show  that  the 
outer  bright-red  layer  varies  in  thickness  within  limits,  with  the  length 


10  HEMOLYMPH    NODES    OF    THE    SHEEP 

of  exposure  to  oxygen,  for  example.  It  was  also  noticed  that  in  winter 
the  color  of  nodes  in  situ  on  the  carcasses  was  darker  than  in  summer, 
which  difference  was  evidently  due  to  the  fact  that  the  severe  cold  of  an 
open  abattoir  in  a  northern  climate  retarded  the  process  of  spontaneous 
post-mortem  oxygenation,  by  making  the  overlying  layers  more  im- 
pervious to  the  oxygen  of  the  air,  or  by  affecting  the  rate  of  chemical 
interchange.  Ordinarily  the  change  in  color  begins  immediately  after 
evisceration,  and  is  noticeable  at  first  in  the  smallest  and  most  exposed 
node.  However,  the  rate  of  the  change  of  color  is  also  dependent  upon 
the  presence  and  the  thickness  of  the  surrounding  layer  of  blood  in  the 
peripheral  blood  space.  That  not  all  nodes  change  from  a  venous  color 
when  the  abdomen  is  opened  to  a  bright  red  upon  exposure  to  the  air 
later  may,  of  course,  be  due  to  these  and  to  other  facts,  as  well  as  to 
variations  hi  thickness  of  the  capsule  and  the  overlying  fat.  An  examina- 
tion of  several  hundred  carcasses  immediately  after  the  abdomen  was 
opened  showed  that  the  variations  in  color  are  very  slight  at  this  time. 
Very  occasionally,  however,  a  small  scarlet  node  is  seen  among  a  group 
of  venous-colored  ones,  which  fact  can  probably  be  explained  by  differ- 
ences in  the  circulatory  conditions  within  the  node.  The  peculiarly  mot- 
tled appearance  of  nodes  which  often  does  not  become  very  evident  until 
fixation  and  hardening,  can  likewise  be  explained  satisfactorily  by  pe- 
culiarities of  structure.  In  these  latter  nodes,  for  example,  the  peripheral 
blood  space  is  encroached  upon  here  and  there  infra  vitam,  and  often  so 
as  a  result  of  shrinkage  during  fixation  and  hardening,  by  the  lymphatic 
tissue — usually  by  follicles — and  may  hence  be  completely  obliterated  at 
some  places.  Wherever  this  occurs  a  gray  patch  or  streak  bordered  by 
a  deeper-colored  area  will  be  found  on  the  surface.  For  like  reasons 
the  entire  absence  of  the  peripheral  blood  space  before  or  after  fixation 
might  give  a  whole  node  a  grayish  color,  or  if  absent  over  but  a  part  of 
the  node  it  might  result  in  an  appearance  which  might  suggest  that  one 
portion  has  the  character  of  a  hemolymph  and  the  other  that  of  a  lymph 
node,  or  that  there  are  mixed  or  composite  nodes.  Besides  these  factors, 
still  others,  to  be  discussed  later,  have  an  important  bearing  upon  the 
question  of  external  appearance. 

Exposure  of  hemolymph  nodes  to  carbon  dioxide,  on  the  contrary, 
never  produced  the  slightest  visible  changes  in  color.  Such  as  were 
chocolate-colored  when  exposed  to  this  gas  remained  so.  The  same  was 
true  if  they  were  of  any  other  shade.  But  if  nodes  thus  exposed  for  a 
short  time  were  still  sufficiently  fresh,  subsequent  exposure  to  oxygen 
would  result  in  a  change  to  the  usual  bright-red  color  of  freshly  coagu- 


DISTRIBUTION,    OCCURRENCE    AND    APPEARANCE  II 

lated  blood.  Exposure  of  fresh  hemolymph  nodes  to  gaseous  hydrogen 
sulphide  in  pure  or  mixed  form,  or  to  weak  or  concentrated  solutions  of 
the  same  in  water,  in  alcohol,  and  to  an  ammonia-alcohol  mixture  con- 
taining hydrogen  sulphide  would,  on  the  contrary,  invariably  result  in  a 
rapid  change  to  an  intensely  black  color.  It  was  also  noticed  that  ex- 
posure of  cut  nodes  in  water  saturated  with  hydrogen  sulphide  caused  a 
more  rapid  change  to  a  deeper  black  than  exposure  in  a  solution  of  80 
per  cent  alcohol  similarly  saturated.  Since  the  latter  solution  con- 
tains much  more  hydrogen  sulphide  than  the  former,  it  is  appar- 
ent that  the  slower  and  less  pronounced  color  change  in  nodes  immersed 
in  it  is  probably  due  to  the  effect  of  shrinkage  and  hardening,  and  per- 
haps also  to  the  dehydrating  effect  of  the  alcohol.  If  they  were  exposed 
to  the  action  of  diluted  instead  of  concentrated  gaseous  hydrogen  sul- 
phide, a  very  gradual  change  to  green  followed  that  to  black,  thus  giving 
the  nodes  a  grayish  color,  as  described  by  Warthin  [36].  Furthermore, 
if  the  freshly  cut  surface  of  a  node  was  thus  exposed,  these  changes  were 
much  more  rapid,  and  the  green  was  frequently  so  deep  that  it  simulated 
black.  Solutions  in  water  of  hydrogen  sulphide  and  of  the  yellow  am- 
monium sulphide,  in  various  concentrations  had  a  similar  action.  How- 
ever, if  immersion  of  the  nodes  in  a  solution  of  sulphide,  free  from  oxy- 
gen, was  complete,  no  change  from  black  to  green  took  place  at  all.  The 
black  color  remained  permanent,  and  was  retained  in  the  alcoholic  hard- 
ening solutions,  as  well  as  in  all  later  processes.  These  facts  suggest,  of 
course,  that  the  change  from  black  to  green  is  indeed  an  oxidation  change 
of  some  sort;  which  conclusion  is  further  confirmed  by  exposure  of 
nodes  to  pure  hydrogen  sulphide,  with  subsequent  exposure  to  pure  car- 
bon dioxide  or  to  oxygen.  Nodes  kept  in  pure  hydrogen  sulphide,  or 
subsequently  exposed  to  carbon  dioxide,  remained  black  for  days. 

As  in  the  case  of  the  color  changes  due  to  oxygen,  the  color  change 
due  to  these  pure  gases  or  mixtures  of  them  was  a  very  superficial  one, 
even  after  prolonged  exposure — for  six  to  eighteen  hours — to  either 
gaseous  hydrogen  sulphide  or  to  a  solution  of  the  same.  Such  exposure 
never  resulted  in  a  color  change  beyond  the  depth  of  one  or  two  milli- 
meters, even  on  the  surface  of  a  freshly-cut  node.  At  greater  depths 
into  the  node  the  original  color  was  retained,  even  for  twenty-four  hours 
or  more,  until  maceration  and  putrefactive  changes  produced  the  usual 
results.  The  same  was  true  regarding  the  apparently  permanent  green 
color  which  followed  the  change  to  black.  If  fresh  nodes  or  pieces  of 
the  same  were  immersed  in  95  per  cent  alcohol  saturated  with  hydrogen 
sulphide,  they  would  undergo  the  usual  color  changes ;  but  after  weeks 


12  HEMOLYMPH    NODES    OF    THE    SHEEP 

or  months  of  immersion  it  was  found  that  both  the  black  and  the  suc- 
ceeding gray  color  had  completely  disappeared,  so  that  the  tissue  had  the 
customary  gray  color  characteristic  of  lymph  nodes  or  of  lymphatic  tissue 
fixed  in  pure  alcohol.  This  change  in  color  occurred  even  if  the  alcohol, 
at  the  time  when  the  tissue  had  lost  the  black  color  which  was  acquired 
through  exposure  to  hydrogen  sulphide,  still  contained  hydrogen  sul- 
phide in  considerable  quantity.  Sometimes  the  alcoholic  solution  con- 
tained a  small  quantity  of  a  dull  black  deposit  after  the  nodes  had  lost  the 
black  color.  This  deposit  or  precipitate,  which  appeared  only  after  weeks 
of  immersion,  was  finely  granular,  and  quickly  sank  to  the  bottom  after 
shaking. 

The  action  of  hydrogen  sulphide  was  comparable  to  that  of  oxygen, 
then,  in  that  its  penetration  was  merely  a  superficial  one,  though  the 
color  change  was  apparently  more  rapid  in  the  case  of  exposure  to  hydro- 
gen sulphide  than  to  pure  oxygen.  This  was  true,  both  when  a  change 
from  dark  venous  to  red,  or  from  a  sulphide-produced  black  to  a  green 
color,  was  concerned;  and  it  may  be  possible,  as  has  been  suggested, 
that  the  jet-black  color  of  nodes,  occasionally  found  post-mortem  in  sheep, 
may  be  due  to  the  action  of  hydrogen  sulphide  formed  in  decomposi- 
tion (  ?)  or  from  other  tissue  changes. 

In  writing  of  the  color  changes  following  exposure  to  hydrogen  sul- 
phide, Warthin  [36]  stated  that  "The  important  point  is  the  fact  that  In 
the  hemolymph  nodes  there  may  be  such  a  quantity  of  iron-containing 
pigment  that  these  nodes  may  take  up  hydrogen  sulphide  and  become 
grayish  or  black  in  color,  while  the  spleen  remains  unchanged."  (The 
italics  are  the  writer's.)  Warthin  further  stated  that  the  combination 
of  hydrogen  sulphide  and  iron  is  probably  the  cause  of  pseudo-melanosis, 
and  added  in  a  footnote  that  "The  exposure  of  hemolymph  nodes  ob- 
tained from  cattle  and  sheep  produced  results  exactly  like  the  autopsy 
findings  in  the  above  cases.  The  nodes  quickly  became  discolored,  some 
becoming  uniformly  grayish-black  or  brownish-black,  others  becoming 
spotted  or  streaked.  The  discoloration  thus  produced  lasted  for  a  longer 
time  than  that  seen  in  human  autopsy  cases."  The  color  changes  re- 
ported by  Warthin  have  been  confirmed  only  as  far  as  gross  appearances 
are  concerned,  for  frequent  microscopical  examination  of  nodes  which 
had  turned  black  spontaneously  or  upon  exposure,  never  revealed  a  pic- 
ture of  pseudo-melanosis,  nor  was  a  single  test  for  iron  in  either  the 
ferrous  or  ferric  forms  ever  positive.  But  I  am  well  aware  that  these 
tests  may  not  be  relied  upon  with  certainty,  and,  moreover,  that  the  iron 
may  be  in  the  organic  form  and  hence  nevertheless  present.  Consequent- 


DISTRIBUTION,    OCCURRENCE    AND    APPEARANCE  13 

ly,  it  might  still  be  true  that  the  change  from  red  to  black  which  is  pro- 
duced by  exposure  of  nodes  to  hydrogen  sulphide,  although  not  directly 
attributable  to,  might  yet  be  accompanied  by  the  presence  of  an  excess 
of  iron  in  hemolymph  nodes.  Although  Warthin's  conclusion  regarding 
the  excess  of  iron  in  hemal  nodes  relies  partly  upon  these  color  changes, 
it  is  interesting  to  report  that  the  fresh  blood  of  any  animal  turns  black 
almost  instantly  on  exposure  to  hydrogen  sulphide.  Evidently,  then 
according  to  Warthin's  reasoning  the  blood  of  a  number  of  domestic 
animals  must  contain  more  iron  even  than  the  hemolymph  nodes  of  these 
same  animals :  a  conclusion  in  direct  contradiction  to  that  of  Warthin. 
Moreover,  it  was  found  that  not  only  the  blood,  but  also  the  spleen, 
muscle,  liver,  blood  vessels — in  fact  any  fresh  vascular  tissue — would 
undergo  identically  the  same  color  changes,  and  do  so  even  more  rapidly 
in  some  cases  than  the  hemolymph  nodes  themselves.  From  these  obser- 
vations it  is  clear  then  that  the  hemolymph  nodes  very  likely  undergo 
these  color  changes  when  exposed  to  hydrogen  sulphide,  simply  because 
they  are  very  vascular;  and  not  necessarily,  as  assumed  by  Warthin, 
because  they  contain  an  excess  of  inorganic  iron.  To  be  sure,  Warthin 
may  be  correct  in  assuming  that  it  is  an  iron  compound  which  produces 
these  changes.  That  is  not  denied  here.  What  concerns  us  is  whether 
or  not  these  color  changes  necessarily  indicate  a  greater  content  of  iron 
on  the  part  of  the  hemolymph  nodes.  That  this  is  not  the  case  the  facts 
cited  seem  to  establish  beyond  all  question.  To  be  sure,  if,  as  has  been 
claimed,  hemolymph  nodes  are  the  seat  of  blood  destruction,  with  result- 
ing decomposition  of  blood  pigment,  it  is  possible,  of  course,  that  they  do 
contain  a  large  or  even  a  larger  amount  of  iron ;  but  the  above  action  of 
hydrogen  sulphides  is  manifestly  .not  a  satisfactory  criterion.  Moreover, 
in  another  article  Warthin  [32]  contradictorily  enough  reported  that  he 
found  but  a  slight  or  no  reaction  for  hemosiderin  in  hemolymph  nodes. 
The  latter  observation,  which  is  contradicted  by  some  investigators, 
agrees  entirely  with  the  findings  of  the  writer;  and  it  seems  possible, 
although  perhaps  not  entirely  probable,  that  differences  in  the  freshness 
of  the  material  may  at  least  in  some  measure  account  for  these  discrepan- 
cies, v  Schumacher  [27]  also  emphasized  the  rare  and  sparse  occurrence 
of  pigment  in  the  hemolymph  nodes  of  sheep. 

Although  there  are  great  variations  in  the  quantity  of  blood  con- 
tained in  hemolymph  nodes,  their  vascularity,  as  judged  by  external 
appearances,  did  not  seem  to  be  affected  by  the  rate  or  thoroughness  of 
bleeding  during  slaughtering.  In  sheep  which  were  bled  slowly  from 
one  carotid  or  jugular  only,  or  in  others  which  were  bled  rapidly  from 


14  HEMOLYMPH    NODES    OF    THE    SHEEP 

both  carotids  and  jugulars  by  severing  all  the  ventral  soft  parts  of  the 
neck,  the  nodes  were  always  found  turgescent.  If  death  occurred  with- 
out bleeding,  there  was  no  marked  difference  save  that  the  veins  draining 
the  nodes  seemed  a  trifle  fuller,  and  the  color  of  the  nodes  a  little  darker ; 
which  latter  fact  may  perhaps  be  accounted  for  by  defective  aeration  of 
the  blood  during  death.  This  failure  of  hemolymph  nodes  to  become 
paler  during  death  by  bleeding  stands  in  striking  contrast  to  what  is 
noticed  in  many  lymph  nodes,  v  Schumacher  [27]  also  emphasized  the 
effect  of  bleeding  upon  the  color  of  lymph  nodes  and  pointed  out  that 
lymph  nodes  in  foetuses  in  which  free  bleeding  is  secured  by  severing  the 
cord,  are  always  much  paler  than  those  in  foetuses  which  are  killed 
without  such  bleeding.  The  significance  of  these  differences  in  behavior 
between  hemolymph  and  lymph  nodes  will  be  discussed  in  connection  with 
the  circulatory  condition  in  the  nodes. 

Since  the  vein  draining  a  node  is  usually  dilated  with  blood,  it  can 
frequently  be  seen  without  difficulty  on  inspection.  In  almost  any  car- 
cass one  or  two  nodes  can  be  found  the  veins  of  which  are  plainly  visible 
from  five  to  ten  centimeters  or  more  from  the  node,  even  if  the  latter 
is  only  a  few  millimeters  in  size.  Anastomoses  with  the  veins  from 
adjacent  nodes  are  quite  common.  The  artery,  on  the  contrary,  is  not 
seen  on  inspection  alone,  no  matter  how  turgescent  or  large  the  node, 
or  how  prominent  the  vein.  Pressure  upon  the  nodes  generally  results 
in  rupture,  without  visibly  dilating  the  vein  or  the  artery  or  decreasing 
the  vascularity  of  the  node.  This  inability  to  force  out  the  blood  by 
means  of  external  pressure  on  the  nodes  was  quite  puzzling,  until  the 
peculiarities  of  their  structure  supplied  an  explanation. 

LYMPHATIC  AND  VASCULAR  RELATIONS     • 

Lymphatic  vessels  were  never  detected  or  dissected  out  in  the  hilus 
of  a  hemolymph  node  however  large,  although  it  was  often  an  easy 
matter  to  see  and  find  them  near  a  lymphatic  node  of  much  smaller  size. 
Frequently  lymphatic  vessels  of  varying  calibre  and  conspicuousness 
could  be  seen  near  hemolymph  nodes,  or  even  in  contact  with  them ;  but 
even  in  the  case  of  very  large  nodes  no  communication  was  ever  noticed 
between  them  and  the  nodes,  upon  the  most  careful  examination.  Hence 
these  observations  confirm  the  conclusion  of  Weidenreich  [37]  in  this 
regard  and  contradict  Kelly's  [n]  statement  to  the  effect  that  lymphatic 
channels  can  be  seen  to  enter  the  hilus  of  the  hemolymph  nodes,  although 
not  found  within  the  node,  and  that  nodes  which  lie  near  large  lymphatics 
contain  such  vessels.  Aside  from  the  difficulty,  or  impossibility  even. 


LYMPHATIC    AND   VASCULAR    RELATIONS  1$ 

of  seeing  a  hilus  macroscopically  in  most  of  these  nodes,  it  is  well  to 
remember  in  this  connection  that  Helly  did  not  state  how  the  lymphatics 
were  identified  positively  as  such.  Moreover,  small  lymphatic  channels 
might  be  confined  wholly  to  the  capsule  of  the  node  or  its  large  trabe- 
culae  without  necessarily  establishing  any  charasteristic  connection  with 
the  parenchyma  of  the  node  itself.  Kelly's  conclusions  and  observations 
are  largely  confirmed,  however,  by  Forgeot  [6  and  7]  and  v  Schumacher 
[27].  The  former  described  nodes  in  the  lumbar  region  of  goats  and 
sheep,  and  under  the  pleura  and  pericardium  of  cattle,  from  which 
blindly-ending  lymphatic  vessels  of  varying  form  extended.  In  some 
cases  these  vessels  returned  to  the  neighborhood  of  the  node  and  were 
markedly  distended  with  red  lymph.  The  several  vessels  were  found  to 
end  blindly  independently,  or  to  be  joined  into  a  network  which  sur- 
rounded a  node  the  main  branches  from  which  formed  a  common  trunk, 
which  also  ended  blindly.  An  examination  of  Forgeot's  articles  show 
very  clearly,  however,  that  he  has  included  "red"  or  hermorrhagic  lymph 
nodes,  i.  e.,  lymph  nodes  with  erythrocytes  in  the  sinuses,  among  hemo- 
lymph  nodes,  an  error  against  which  v  Schumacher  rightly  warns,  and 
which  has  undoubtedly  been  responsible  for '  much  of  the  confusion. 
Nevertheless  v  Schumacher,  who  largely  accepted  and  confirmed  the 
conclusions  and  observations  of  Helly  and  Forgeot,  basing  his  con- 
clusions on  an  examination  of  adult  and  embryological  material  from  the 
sheep,  emphasized  the  fact  that  hemolymph  nodes  usually  lie  in  the  neigh- 
borhood of  large  lymph  vessels,  and  that  branches  of  the  latter  frequent- 
ly extend  considerable  distances  into  the  capsule  without  piercing  the 
latter  or  coming  into  relation  with  the  marginal  sinus.  Sometimes  such 
lymphatic  vessels  were,  however,  seen  to  join  the  sinus,  and  these  nodes 
v  Schumacher  excludes  from  hemolymph  nodes,  on  the  opinion  of  others. 
Nevertheless  v  Schumacher  proceeds  to  state  that  all  manner  of  transi- 
tion forms  between  lymph  and  hemolymph  nodes  exist  as  far  as  the  rela- 
tion of  the  lymphatics  to  the  nodes  are  concerned,  and  describes  nodes 
with  lymphatic  vessels  in  process  of  obliteration  in  different  places  with- 
in and  without  the  nodes,  much  as  Helly  has  done,  v  Schumacher  also 
came  to  the  conclusion  that  hemolymph  nodes  are  only  rudimentary  or 
undeveloped  lymph  nodes  which  have  lost  their  connection  with  the  lym- 
phatic system  as  a  result  of  the  obliteration  of  the  lymphatics  at  various 
points.  Consequently,  according  to  v  Schumacher,  a  lymph  node  may 
become  a  hemolymph  node  by  losing  its  lymphatics,  and  can  again  be- 
come a  lymph  node  by  regaining  them.  Since  these  conceptions  and  con- 
clusions are  based  partly  upon  developmental  considerations,  they  will 


l6  HEMOLYMPH    NODES    OF    THE    SHEEP 

be  discussed  especially  in  a  separate  article  on  this  subject;  but  it  may 
here  be  noted  that  the  conclusion  that  a  true  hemolymph  node  is  merely 
a  lymph  node  devoid  of  lymphatic  vessels  and  sinuses,  is  only  possible 
upon  a  fundamental  misconception  of  the  real  character  of  the  vascular 
circulation  of  true  hemal  nodes. 

These  considerations  at  once  raise  the  question  of  the  relation  be- 
tween hemolymph  nodes  and  the  lymphatic  system.  In  order  to  deter- 
mine whether  a  direct  connection  exists  between  them,  injection  methods 
seemed  to  offer  the  best  and  perhaps  the  only  positive  proof.  Since  an 
abundant  supply  of  material  could  be  found  in  the  carcasses  of  sheep, 
the  abattoir  again  suggested  itself  as  an  especially  good  field  for  this 
work.  Hence'  many  hundreds — thousands — of  injections  were  made 
directly  into  the  nodes  upon  the  fresh  carcasses.  Occasionally  this  was 
within  ten  minutes  or  a  quarter  of  an  hour  after  death.  The  results  ob- 
tained by  means  of  puncture  injections  with  a  hypodermic  syringe  into 
the  nodes  practically  undisturbed  in  situ  in  the  lumbar  region,  were  sur- 
prisingly uniform.  As  node  after  node  on  the  hanging  carcasses  was 
punctured  and  injected,  the  invariable  result  of  the  injection  of  a  few 
drops  of  methylene  blue,  Prussian  blue,  India  ink,  etc.,  was  the  almost 
immediate  appearance  of  the  fluid  in  the  vena  cava,  or  occasionally  in  the 
common  iliac  veins.  Since  the  appearance  of  even  a  fraction  of  a  drop 
of  the  colored  solutions  or  suspensions  quickly  became  evident  in  the  col- 
lapsed veins,  it  was,  to  be  sure,  an  easy  matter  to  decide  between  suc- 
cess and  failure.  To  avoid  error  many  hundreds  of  injections  were  made 
into  nodes  of  various  sizes,  shapes,  colors,  and  positions  in  the  abdominal 
and  thoracic  cavities  of  sheep  from  a  few  weeks  to  four  or  five  years  old. 
By  far  the  greatest  number  of  these  injections  were  made  on  the  lumbar 
group,  however. 

v  Schumacher,  who  agreed  with  Weidenreich  and  the  writer  as  to 
the  injections  of  the  vein  by  means  of  puncture  of  the  node,  however, 
emphasized  the  fact  that  he  obtained  such  a  result  by  no  means  in  every 
case,  but  only  when  one  of  the  intra-nodal  veins  was  pierced.  In  numer- 
ous instances  v  Schumacher  found  that  only  the  sinuses  in  the  interior 
of  the  gland  were  filled,  and  whenever  the  vein  leaving  the  node  was  in- 
jected v  Schumacher  says  he  could  always  tell  by  serial  sections  that  a 
vein  in  the  interior  of  the  gland  had  been  punctured  by  the  needle,  so 
that  the  injection  mass  could  pass  directly  into  the  large  collecting  veins 
at  the  hilus. 

I  am  at  a  loss  to  account  for  v  Schumacher's  failure  to  inject  the 
veins  of  hemal  nodes  in  practically  all  cases  by  means  of  puncture  of  the 


LYMPHATIC    AND   VASCULAR    RELATIONS  17 

node.  To  be  sure,  the  choice  of  nodes  is  of  primary  importance,  and  no 
one  can  be  positive  that  he  has  selected  a  hemal  node  if  he  fails  to  inject 
the  vein  or  lymphatics.  Besides,  no  one  will  doubt  that  a  venous  radicle 
must  have  been  penetrated  by  the  needle  or  its  wall  penetrated  by  the  in- 
jection mass,  if  the  vein  leaving  the  node  is  filled ;  but  after  examining 
numerous  nodes  which  had  been  injected  by  puncture,  I  must  entertain 
the  gravest  doubts  as  to  the  possibility  of  determining  the  exact  point 
of  puncture  of  a  venous  lacunae.  For  even  the  smallest  needle  or  capil- 
lary glass  tube  bears  a  marked  disproportion  to  the  size  of  the  numerous 
venous  radicles  in  a  node.  Besides,  it  would  be  likely  to  pierce  so  many 
— or  none — for  most  of  the  hemal  nodes  are  small,  as  v  Schumacher 
rightly  emphasizes.  Hence  locating  the  exact  point  of  puncture  of  the 
wall  of  a  particular  venous  lacuna  through  which  the  injection  mass  is 
supposed  to  have  entered,  must  be  open  to  serious  error,  even  if  possible. 
Moreover,  veins  are  not  always  present  within  a  node ;  venous  lacunae  or 
sinuses  take  their  place  frequently. 

It  was  generally  very  easy  to  see  the  injected  fluid  pass  from  the 
hemolymph  node  to  the  vena  cava,  pushing  the  blood  in  the  vein  leaving 
the  node  before  it.  As  more  fluid  was  injected,  a  steady  stream,  some- 
times inter-mixed  with  blood  and  bubbles,  could  be  seen  passing  to  the 
vena  cava  or  the  iliac  veins.  Frequently  the  injected  fluid  would  pass 
in  a  somewhat  roundabout  way  to  reach  its  destination  in  the  large  veins  ; 
and  occasionally  it  would  leave  the  node  in  two  directions  from  the  same 
or  from  different  points.  Clamping  of  the  vein  on  its  way  to  the  vena 
cava  led  to  rupture  of  the  node  upon  further  injection,  but  not  to  the  in- 
jection of  lymphatics.  Anastomosing  veins  would  occasionally  become 
filled  with  fluid ;  but  several  times  only  did  an  adjacent  or  distant  node 
seem  to  change  its  color  very  slightly.  For  a  time  this  inability  to 
inject  one  node  from  another  in  the  fresh  hanging  carcasses  was  very 
puzzling,  for  it  was  evident  that  the  veins  from  several  nodes  not  infre- 
quently joined  on  their  way  to  the  vena  cava.  Besides,  it  will  be  recalled 
that  Weidenreich  [37]  reported  that  it  was  easy  to  inject  a  node  from  a 
neighboring  one.  This  apparent  contradiction  of  Weidenreich's  results 
was  emphasized  further  by  the  fact  that  it  was  never  possible  to  inject 
secondarily  smaller  hemolymph  nodes  which  lay  in  actual  contact  with 
the  larger  ones,  from  which  the  injection  was  made.  This  was  true,  even 
when  it  was  afterwards  found  by  injection  of  differently  colored  fluids 
from  the  individual  nodes  concerned  that  they  were  drained  by  branches 
of  the  same  vein.  Naturally  the  fact  that  small  veins  draining  hemolymph 
nodes  are  usually  full  of  blood,  suggested  that  the  failure  to  inject  one 


l8  HEMOLYMPH    NODES    OF    THE    SHEEP 

node  from  another  probably  was  mainly  due  to  the  presence  of  blood, 
and  to  some  condition  within  the  nodes  which  prevented  a  re-flow  of 
this  blood  to  the  arterial  side.  Such  conditions  alone,  it  seemed,  could 
explain  the  above  facts,  for  a  system  of  filled  tubes  could  naturally  not 
receive  more  fluid  without  further  distention  of  the  vessels  of  the  node, 
or  of  leakage  or  rupture.  Consequently,  the  fat  in  the  lumbar  region, 
including  the  great  vessels,  containing  especially  numerous  nodes,  was 
excised  en  masse,  as  Weidenreich  had  done.  By  means  of  puncture  in- 
jections of  the  nodes  it  was  now  found  a  very  easy  matter  to  force  the 
injected  fluids  into  adjacent  or  occasionally  distant  nodes,  even  if  the 
flow  toward  the  excised  vena  cava  was  unobstructed.  Hence  Weiden- 
reich's  observations  were  easily  confirmed  by  using  similar  methods. 
But  these  results  now  required  an  explanation ;  for  why  should  there  be 
such  difficulty  in  injecting  one  node  from  another  with  the  nodes  un- 
disturbed in  situ  in  the  carcasses?  Although  I  have  no  wholly  satis- 
factory explanation,  it  is  probable,  it  seems  to  me,  that  the  manipulation 
incident  to  excision  of  the  tissue  emptied  the  veins  which  drained  the 
nodes,  sufficiently  to  permit  the  injected  fluid  to  enter.  Besides,  as  shown 
by  the  many  points  of  leakage  when  injections  were  made  into  nodes 
contained  in  excised  tissue,  the  numerous  anastomosing  veins  which  are 
severed  during  removal  of  the  tissue  also  gave  opportunity  for  relief  of 
pressure  in  several  directions.  Hence  the  condition  of  a  system  of  closed 
tubes  partially  or  totally  filled  with  fluid  no  longer  existed.  It  is  evident, 
of  course,  that  it  is  not  essential  that  the  vein  which  drains  a  node  be 
completely  full  of  blood  to  prevent  the  injected  fluid  from  entering 
the  node,  or,  on  the  contrary,  that  it  and  the  node  must  be  com- 
pletely empty  before  any  injection  mass  can  enter.  All  that  is  mani- 
festly necessary  is  that  a  sufficient  quantity  of  blood  be  contained  in  the 
main  or  in  the  anastomosing  veins  to  completely  fill,  or  perhaps  to  suf- 
ficiently distend,  the  venous  spaces  within  the  node  to  make  further  in- 
jection impossible.  For  in  case  of  a  small  node  even  a  fraction  of  a  drop 
of  blood  in  advance  of  the  injected  fluid  might  effectually  prevent  a  suc- 
cessful injection,  unless  the  veins  and  venous  spaces  within  the  node  are 
partially  or  totally  empty.  Since  these  conditions  probably  obtain  more 
or  less  in  excised  tissue,  it  was  possible  to  inject  a  series  of  three  or  four 
nodes  lying  in  a  row  from  one  of  their  number,  with  a  few  drops  of 
fluid.  It  was  also  occasionally  possible  to  inject  incidentally  a  network 
of  minute  retro-peritoneal  veins — not  lymphatics — from  nodes  in  the  ex- 
cised tissue;  although  such  a  result  was  never  obtained  in  the  many 
injections  made  directly  into  nodes  in  situ  on  carcasses.  These  veins, 


LYMPHATIC    AND   VASCULAR    RELATIONS  19 

which  after  being  injected  formed  a  network  of  the  greatest  delicacy, 
were  so  fine  that  they  were  barely  visible  to  the  unaided  eye. 

In  a  large  series  of  puncture  injections,  it  was  never  possible  to  in- 
ject a  lymphatic  vessel  or  a  lymph  node  from  a  hemolymph  node  unless 
the  point  of  the  needle  pierced  the  hemolymph  node,  thus  allowing  the 
injected  fluid  to  enter  the  retro-peritoneal  tissues.  A  series  of  puncture 
injections  made  into  the  surrounding  tissues  and  body  wall  proved  equal- 
ly ineffectual  for  injecting  the  hemolymph  nodes  or  blindly  ending  lym- 
phatics. Both  lymphatic  vessels  and  lymph  nodes,  on  the  contrary,  were 
injected  comparatively  easily  by  either  of  these  methods,  and  injections 
into  lymph  nodes  always  led  to  the  well-known  results.  The  usually 
characteristically  beaded  lymphatic  channels  were  instantly  apparent, 
other  lymph  nodes  were  injected,  and  the  injected  fluid  soon  ran  out  of 
the  cut  end  of  the  thoracic  duct  in  the  cervical  region,  just  as  it  had 
previously  run  out  of  the  vena  cava  in  the  thoracic  region.  Nor  did  the 
injection  of  some  unusually  large — 3-4  mm. — lymphatic  channels  occa- 
sionally seen  in  the  lumbar  region,  result  in  the  injection  of  anything  but 
lymph  channels  and  lymph  nodes.  In  three  carcasses,  for  example,  espe- 
cially large  lymph  channels  three  to  four  millimeters  in  diameter  lay 
superficially  among  a  group  of  hemolymph  nodes  in  the  lumbar  region. 
The  injection  by  puncture  of  methylene  blue  into  these  large  lymph  ves- 
sels, even  when  the  thoracic  duct  had  been  clamped  and  lymph  nodes  on 
all  sides  were  injected  both  peripherally  and  centrally,  resulted  negative- 
ly, as  before,  as  far  as  injection  of  hemolymph  nodes  is  concerned,  even 
when  high  pressure  was  used.  Hemolymph  nodes,  on  the  other  hand, 
were  never  injected,  even  if  they  lay  side  by  side  with  or  directly  upon 
or  beneath  injected  lymph  nodes;  and  not  a  trace  of  the  injection  was 
ever  found  in  them  upon  microscopical  examination. 

The  facts  just  cited,  together  with  others  to  be  considered,  prove 
conclusively,  it  seems  to  me,  that,  as  maintained  by  Weidenreich  [38], 
the  circulation  of  true  hemolymph  nodes,  exclusive  of  the  capsule  at 
least,  has  no  connection  whatever  with  the  lymphatic  system.  They 
prove  further  that  there  probably  are  no  nodes  of  a  mixed  type  having 
sinuses  common  to  the  vascular  and  lymphatic  systems,  and  that  conse- 
quently the  word  hemolymph  is  a  misnomer  when  applied  to  these  nodes 
of  the  sheep.  Since,  then,  all  these  so-called  hemolymph  nodes  are  solely 
in  direct  connection  with  the  vascular  system  alone,  and  contain  no 
lymph  spaces,  the  designation  of  hemal  node  first  used  by  Clarkson  [2] 
is  preferable,  and  will  hence  be  used  in  this  discussion. 

Since  these  results  seemed  to  indicate  that  hemal  nodes  are  entirely 


2O  HEMOLYMPH    NODES    OF    THE    SHEEP 

independent  of  the  lymphatic  system,  injections  were  also  made  from  the 
abdominal  vena  cava  and  aorta,  in  order  to  determine  whether  the  spaces 
found  in  hemal  nodes  are  in  direct  connection  with  these  vessels.  Such 
injections  were  made  on  two  lambs  seven  to  eight  months  and  four  to 
six  weeks  old,  and  six  foetuses  from  four  to  five  months  old.  Three  of 
-these  lambs  were  bled  to  death.  In  case  of  the  other  lamb  and  the 
foetuses,  some  relief  from  back  pressure  due  to  the  contained  blood  was 
secured  by  incision  of  the  vena  cava.  Injections  of  filtered  carmine  and 
Prussian  blue  gelatine  were  made  directly  into  the  abdominal  portions 
of  these  vessels.  The  carcasses  were  kept  immersed  in  warm  water  and 
a  high  uniform  pressure  (200-250  mm.  Hg.)  was  maintained  continuous- 
ly for  a  period  of  one-half  to  three-fourths  of  an  hour.  Besides  this, 
the  injection  was  limited  as  far  as  possible  to  the  lumbar  region  by 
clamping  the  main  branches  of  the  great  vessels.  Since  the  injection 
mass  was  thus  limited  to  a  small  field,  the  behavior  of  the  hemal  and 
lymphatic  nodes  could  be  observed  more  carefully  during  the  progress 
of  the  injection.  Although  at  first  it  was  attempted  to  mark  the  site  of 
some  of  the  typical  hemal  nodes,  by  transfixing  the  adjacent  tissue  with 
a  small  pin,  the  high  pressure  used  on  the  filtered  gelatine  caused  con- 
siderable leakage  at  the  point  of  puncture,  which  threatened  to  obscure 
the  field.  Hence  this  method  was  abandoned. 

(Upon  completion  of  the  injections,  the  bodies  of  the  foetuses  were 
cooled,  and  fixed,  in  toto,  in  formaline.  In  case  of  the  lambs,  the  whole 
lower  half  of  the  body  was  likewise  preserved,  in  order  to  leave  the  area 
under  observation  undisturbed.  All  nodes  were  later  dissected  out  by 
means  of  a  lens  when  necessary,  and  cut  serially  in  paraffine.  It  was 
found  advisable  to  remove  all  nodes  found  in  a  given  area,  because  of 
the  difficulty,  or  impossibility  even,  of  distinguishing  injected  hemal  and 
lymphatic  nodes  by  external  appearances. 

During  the  course  of  the  injection  it  was  disappointing  to  notice 
how  quickly  even  the  smallest  lymph  nodes,  distant  often  from  the  place 
of  injection,  would  quickly  change  their  color  due  to  entrance  of  the 
injection  mass,  while  much  larger  near-by  typical — as  judged  by  external 
appearances — hemal  nodes  showed  no  color  change  whatever.  That  this 
apparent  failure  to  inject  the  great  majority  of  the  hemal  nodes  was  not 
due  to  a  faulty  technique,  was  shown  by  the  fact  that  the  whole  carcasses 
were  so  well  injected,  in  spite  of  ligation  of  the  main  branches  of  the 
great  vessels,  that  even  the  small  parathymus  glands  had  changed  their 
color  and  were  found  on  microscopic  examination  to  contain  much  injec- 
tion mass. 


LYMPHATIC    AND   VASCULAR    RELATIONS  21 

Before  giving  a  statement  of  the  results  obtained  by  these  injections, 
a  rough  sketch  of  the  microscopic  structure  of  the  more  usual  hemal 
nodes  seems  advisable.  In  the  majority  of  these  nodes,  a  view  of  a  sec- 
tion made  in  any  plane  presents  the  following  well-known  appearances. 
Externally  there  is  a  fibrous  capsule  varying  considerably  in  thickness 
in  the  same  and  in  different  species,  beneath  which  there  usually  is  found 
a  continuous  or,  oftener,  a  discontinuous  so-called  peripheral  sinus,  of 
inconstant  width,  which  generally  contains  more  or  less  blood  and  lym- 
phocytes. As  a  rule,  by  far  the  larger  area  of  the  node  is  composed  of 
lymphatic  tissue,  containing  the  well-known  blood  sinuses,  or  better, 
blood  islands  or  spaces.* 

A  definite  cortical  and  medullary  portion,  or  an  arrangement  of  the 
lymphatic  tissue  into  medullary  cords,  was  never  seen.  The  arteries  are 
inconspicuous  as  a  rule,  and  the  veins  frequently  still  more  so.  In  addi- 
tion to  the  inconstant,  large  central  venous  spaces  in  direct  connection 
with  veins  more  or  less  evident  partially  collapsed  or  open  spaces,  the 
so-called  venous  lacunae  of  Weidenreich  may  also  be  present  through- 
out the  parenchyma.  When  evident  they  are  usually  best  seen  near  the 
periphery  of  the  parenchyma,  and  frequently  contain  a  small  number  of 
erythrocytes  and  lymphocytes,  the  former  often  being  found  in  varying 
states  of  degeneration.  The  blood  islands  and  spaces  other  than  the 
peripheral  or  subcapsular  blood  space,  and  the  main  arteries,  often  have 
a  more  central  position,  however ;  but  the  veins  generally  branch  soon 
after  entering  the  node  and  traverse  the  peripheral  sinus,  or  better  the 
marginal  or  subcapsular  blood  space.  Although  rarely  noticeable 
throughout  the  node,  the  trabeculae  are  few  and  small,  as  a  rule.  The 
coarser  reticulum  is  plainly  visible  under  low-power  magnification,  and  is 
more  evident  in  the  partially  filled  blood  spaces,  especially  in  the  marginal 
one.  Since  this  sketch  is  to  serve  merely  as  a  basis  for  a  statement  of 
results  obtained  by  injection,  a  more  detailed  and  accurate  statement  of 
structural  variations  and  relations  is  deferred. 

Injections  made  from  the  vena  cava,  and  by  puncture  from  a  node, 
always  gave  a  very  characteristic  and  uniform  result.  No  matter  how 
little  of  the  injected  fluid  gained  access  to  the  node,  it  almost  always  lay 
as  an  exceedingly  irregular  mass,  often  of  minute  breadth,  which  zig- 

*Since  the  blood  islands  are  usually  masses  of  erythrocytes  contained  in  the 
lymphatic  tissue,  rather  than  empty  spaces  temporarily  devoid  of  blood,  although 
such  undoubtedly  occur,  the  term  blood  space  might  preferably  be  restricted  to  the 
empty  areas,  which  once  contained  blood  islands ;  and  since  neither  of  these  nor  the 
peripheral  sinus  are  really  such,  the  term  sinus  had  better  be  restricted  to  the  dilated 
venous  radicles  in  direct  connection  with  the  circulation. 


22  HEMOLYMPH    NODES    OF    THE    SHEEP 

zagged  about,  but  small  amounts  of  which  were  but  seldom  found  in  the 
peripheral  or  central — in  the  sense  of  internal — blood  islands  or  blood 
spaces.  (Fig.  2.)  However,  if  the  injection  was  a  fairly  complete  one, 
the  gelatine  mass  or  the  India  ink  was  distributed  quite  uniformly 
throughout  the  node,  and  some  of  it  was  rarely  found  within  the  follicles ; 
although  instead  of  penetrating  these,  it  usually  surrounded  them.  In 
some  places,  the  masses  of  injected  material  formed  an  incomplete  and 
a  very  irregular  circuit,  parallel  and  internal  to  the  peripheral  blood 
space,  which  was,  however,  always  separated  from  the  former  by  a  very 
thin  barrier  of  lymphatic  tissue.  In  case  of  injections  of  India  ink  by 
puncture,  the  resulting  picture  was  always  similar  to  that  obtained  by 
injections  from  the  vena  cava;  but  since  the  puncture  injections  were 
generally  much  completer,  a  greater  amount  of  injection  material  was 
present.  In  these  instances  some  of  it  was  found  in  the  peripheral  blood 
space  (sinus),  in  some  of  the  blood  islands,  and  not  infrequently  in  some 
of  the  follicles  as  well.  These  puncture  injections,  whether  made  direct- 
ly into  a  node  or  indirectly  into  an  adjacent  one,  were,  of  course,  also 
venous  injections  (figs.  5  and  6).  Strangely  enough,  out  of  scores  of 
nodes  injected  from  the  venous  side,  only  a  few  showed  the  injection 
mass  lying  in  large  blood  spaces  in  the  center  of  the  node.  In  two  cases 
of  injection  by  puncture,  the  India  ink  also  found  its  way  into  an  artery 
lying  near  a  vein,  wholly  outside  of  a  node.  In  the  latter  cases  it  seems 
likely  that  the  ink  entered  the  outlying  artery  through  accidental  punc- 
ture of  one  of  its  branches  within  the  node,  rather  than  by  passing  from 
the  larger  blood  sinuses  or  lacunae  into  a  capillary  or  an  arteriole  and 
then  to  the  parent  trunk.  Unfortunately,  however,  the  material  at  hand 
does  not  justify  a  definite  conclusion  regarding  these  rare  accidental 
results. 

Carmine  gelatine  injections  from  the  aorta  gave  very  similar  re- 
sults. (Fig.  7.)  If  the  injection  of  the  node  was  only  a  partial  one, 
however — as  was  usually  the  case — the  injected  mass  was  found  mainly 
in  the  venous  lacunae  at  the  periphery,  and  to  a  far  less  extent  near  the 
center  of  the  node.  Hence  in  the  case  of  a  complete  injection  it  would 
be  difficult  indeed  to  distinguish  an  arterial  from  a  venous  injection,  were 
it  not  for  the  fact  that  in  the  former  the  main  arteries  and  their  branches, 
and  frequenly  some  arterioles  and  capillaries,  are  well  injected,  thus  mak- 
ing differentiation  comparatively  easy.  Arterial  injections  from  the 
aorta  also  differed  from  most  of  the  venous  injections  made  by  puncture, 
in  the  fact  that  the  injection  mass  seemed  to  penetrate  the  filled  blood 
spaces  with  more  difficulty.  This  result  may  have  been  due,  however, 


LYMPHATIC    AND    VASCULAR    RELATIONS  23 

to  the  differences  in  pressure  and  to  interference  with  the  architecture  of 
the  node  by  the  puncture  in  case  of  direct  puncture  injections,  as  well  as 
to  other  things  to  be  discussed  presently.  Unfortunately,  none  of  the 
nodes  injected  from  the  aorta  had  a  sufficiently  definite  peripheral 
(sinus)  blood  space  to  afford  good  evidence  regarding  its  relation  to  the 
arteries.  That  the  injection  mass  could  have  entered  the  peripheral 
(sinus)  blood  space  follows,  however,  from  the  fact  that  the  latter  al- 
ways contains  more  or  less  blood.  Hence  both  it  and  the  central  blood 
spaces  must,  to  be  sure,  communicate  in  some  manner  with  the  vascular 
system,  even  if  not  directly  with  it  as  a  rule,  or  with  the  artery. 

The  most  significant  result  obtained  from  these  injections  was  that 
the  so-called  venous  lacunae  or  radicles  could  generally  be  injected  from 
both  the  vena  cava  and  from  the  aorta.  It  is  true  that  these  injections 
were  not  of  equal  completeness,  and  also  varied  in  certain  other  minor 
respects;  yet  the  above  fact  seems  to  demonstrate  conclusively  that  the 
venous  lacunae,  or  true  venous  sinuses  of  the  hemal  nodes  of  the  sheep, 
occupy  a  position  intermediate  between  the  veins  and  the  arteries,  and 
hence  bridge  a  gap  between  them.  However,  as  already  stated,  the  fact 
that  the  blood  spaces  are  more  easily  injected  by  puncture  than  from  the 
aorta,  can  readily  be  explained  by  the  fact  that  higher  pressures  were 
undoubtedly  used,  that  a  more  direct  and  sudden  entrance  of  the  injec- 
tion mass  is  effected,  that  the  architecture  of  the  node  may  be  seriously 
disturbed,  and  that  the  needle  may  happen  to  stop  in  the  parenchyma,  in 
the  case  of  direct  puncture  injections.  Moreover,  in  case  of  injections 
from  the  aorta  the  injection  mass,  which  enters  slowly  through  the 
artery,  can  pass  directly  onward  into  the  wide  venous  lacunae  and  large 
veins,  without  producing  any  appreciable  back  pressure  in  them,  because 
of  the  difference  in  calibre  between  the  arterial  capillaries  and  venous 
sinuses.  Hence  the  injection  is  likely  to  be  incomplete.  That  the  injec- 
tion masses  or  the  pigment,  are  generally  found  in  the  venous  lacunae 
or  true  sinuses,  and  not  in  the  blood  islands  and  spaces,  is  explained  by  the 
fact  that  the  former  are  usually  empty  spaces,  with  permanent  walls 
which,  although  usually  in  a  state  of  total  or  partial  collapse,  are  direct- 
ly connected  with  the  arteries,  and  hence  offer  far  less  obstruction  to  the 
entrance  of  the  injection  mass  than  the  blood  spaces.  The  latter  are  tra- 
versed by  reticulum  and  are  filled  with  blood  which  has  no  easy  and  free 
means  of  escape.  Furthermore,  the  communication  between  the  venous 
lacunae  and  blood  spaces  is,  as  a  rule,  only  an  indirect  one. 

The  great  irregularity  in  shape  of  the  injection  masses  and  the  pig- 
ments, in  both  arterial  and  venous  injections,  somewhat  suggested  extrava- 
sations. This  was  probably  due  to  the  necessarily  incomplete  nature  of 


24  HEMOLYMPH    NODES    OF    THE    SHEEP 

these  injections ;  and  that  they  were  not  extravasations  is  shown  by  the 
entire  absence  of  points  of  rupture,  and  by  the  identical  character  of  the 
injection  masses  in  nodes  injected  indirectly  from  an  adjacent  one,  under 
conditions  of  free  outflow  to  the  vena  cava  through  the  vein  common  to 
several  nodes.  For  under  such  conditions  serious  structural  derange- 
ment is  avoided,  or  at  least  made  improbable,  because  excessive  pressures 
cannot  be  produced  if  the  entrance  of  the  injection  mass  is  a  very  grad- 
ual and  gentle  one.  The  irregularity  in  form  of  the  injection  mass  is 
further  accounted  for  by  the  fact  that  the  venous  lacunae  or  true  sinuses 
are  encroached  upon  to  a  varying  extent  by  the  surrounding  parenchyma, 
thus  offering  different  amounts  of  obstruction  to  the  onward  flow  of  the 
injection  masses  or  fluids;  and  by  the  fact  that  a  partial  injection  of  such 
wide,  irregular  channels  must  of  necessity  vary  greatly  in  calibre. 

The  partial  character  of  the  injections  in  hemal  nodes  injected  from 
the  arterial  side  can  be  accounted  for  by  the  fact  that  the  path  of  least 
resistance  is  undoubtedly  in  the  direction  of  intra-vitam  flow.  Hence 
the  injection  mass  can  easily  enter  some  empty  venous  lacuna  or  sinus, 
and  pass  directly  into  the  vein  or  the  larger  venous  radicles,  rather  than 
flow  from  one  lacuna  to  another,  until  all  or  almost  all  are  filled.  Conse- 
quently it  happens  that  only  a  sufficient  number  of  venous  lacunae  may 
be  injected  to  conduct  the  injection  mass  away  as  fast  as  it  enters  through 
the  artery.  Since  both  the  arterioles  and  capillaries,  and  to  a  less  extent 
also  the  venous  lacunae,  are  usually  in  a  state  of  partial  or  total  collapse 
and  more  or  less  encroached  upon  by  the  parenchyma,  they  naturally  offer 
varying  resistances  to  the  injection  mass.  Consequently  limitation  of  it 
to  certain  lacunae  is  further  promoted.  The  injection  of  the  venous 
lacunae  which  lie  at  the  periphery  of  the  node  in  the  lymphatic  tissue, 
directly  internal  to  the  peripheral  or  subcapsular  blood  space,  to  the  ex- 
clusion of  those  more  centrally  located,  can  be  explained  by  the  fact  that 
the  vein  is  often  in  more  direct  connection  with  them,  as  shown  in  fig.  8 ; 
and  that  as  it  leaves  the  node  it  rarely  receives  a  number  of  tributaries 
which  encircle  the  node,  pierce  the  capsule,  enter  the  lymphatic  tissue, 
and  open  directly  into  these  lacunae  near  the  periphery.  The  presence  of 
accessory  or  accessory  tributary  veins  also  can  explain  why  only  a  very 
small  portion  of  a  section  of  a  node  may  contain  injection  mass,  and  why 
the  injected  fluid,  in  case  of  puncture  injections,  can  rarely  be  seen  to 
leave  the  punctured  node  in  several  directions. 

In  those  instances  of  venous  injections  in  which  some  of  the  central 
or  internal  and  the  peripheral  blood  spaces  contain  injection  mass,  the 
path  taken  by  the  latter  can  usually  be  found  easily  in  numerous  places. 


LYMPHATIC    AND   VASCULAR    RELATIONS  25 

These  paths  apparently  always  lie  through  a  narrow  barrier  of  lymphatic 
tissue  between  venous  lacunae  and  the  blood  spaces.  It  follows  from 
this,  and  from  other  considerations,  that  the  peripheral  and  central  blood 
spaces  or  islands  are  not  necessarily,  or  even  usually,  in  direct  open  com- 
munication with  the  venous  system  in  many  nodes.  Hence  it  is  easy  to 
understand  why  color  changes  are  not  more  manifest  in  hemal  nodes  dur- 
ing the  progress  of  injections  from  the  vena  cava  or  aorta  or  during 
bleeding,  and  why  pressure  exerted  upon  isolated  excised  nodes  does  not 
empty  the  filled  blood  spaces.  Moreover,  it  also  helps  to  explain  why,  in 
case  of  puncture  injections,  the  injected  fluid  is  usually  seen  in  the  vena 
cava  before  any  recognizable  change  in  appearance  of  the  node  takes 
place,  if  the  injection  is  made  slowly  enough.  The  probable  correctness 
of  this  explanation  is  further  confirmed  by  the  results  obtained  by  injec- 
tion in  series  of  a  number  of  nodes  lying  in  a  row  in  excised  tissue,  by 
puncture  from  the  largest  of  them.  When,  for  example,  nodes  i,  2,  3 
and  4,  having  a  common  effluent,  were  injected  with  India  ink  from 
node  i  under  a  free  outflow,  a  sequence  of  events  was  observed  as  fol- 
lows .  The  vein  draining  the  adjoining  nodes  and  tributary  to  the  vein 
draining  node  i,  also  became  filled.  Now  if  these  nodes  and  their  veins 
form  a  series  of  decreasing  size,  the  resistances  offered  to  the  inflow  cf 
ink  necessarily  vary;  and  hence  it  may  happen,  as  was  actually  the  case, 
that  node  2  becomes  injected  before,  and  more  completely  than  nodes 
3  and  4.  Consequently,  node  2  showed  external  color  changes,  while  3 
and  4  did  not  do  so,  or  did  so  but  slightly.  On  cutting  such  an  injected 
series,  it  was  found  that  in  node  2,  which  had  turned  black,  the  ink  had 
penetrated  into  the  peripheral  and  some  of  the  central  blood  spaces,  as 
shown  in  fig.  6.  In  node  3,  on  the  contrary,  which  had  undergone  no 
color  change,  the  ink  was  confined  entirely  to  the  venous  lacunae  or  true 
venous  sinuses ;  while  practically  no  ink  at  all  had  entered  node  4,  which 
had  likewise  undergone  no  color  changes.  It  is  evident,  however,  that 
an  outward  change  in  color  would  occur  in  all  nodes,  whether  they  con- 
tained a  peripheral  blood  space  or  not,  if  a  sufficient  quantity  of  the  in- 
jection mass  penetrated  the  node. 

It  follows,  from  these  facts,  that  it  is  generally  very  easy  to  dis- 
tinguish between  an  arterial  and  a  venous  injection  from  sections  of  in- 
jected nodes ;  and  I  fail  to  see  why  Drummond  declared  it  to  be  impos- 
sible to  do  so.  This  would  be  true  even  in  the  case  of  a  venous  injection, 
in  which  the  lacunae,  the  blood  spaces,  and  the  veins  were  entirely  empty 
before  injection ;  for  in  such  a  case  the  arteries  would  remain  unin- 
jected,  which  would  not  be  the  case  if  the  injection  had  been  made  from 


26  HEMOLYMPH    NODES    OF    THE    SHEEP 

the  arterial  side.  It  is  usually  just  as  easy  to  distinguish  an  injected 
hemal  from  a  lymphatic  node  injected  from  the  vascular  system;  unless, 
perhaps,  some  difficulty  might  be  experienced  in  case  of  a  lymph  node  in 
which  extravasation  of  the  injection  mass  into  the  parenchyma  or  lym- 
phatics had  occurred.  For,  aside  from  the  fact  that  small  lymph  nodes 
readily  manifest  color  changes,  the  injection  mass  as  a  rule  entirely  fills 
the  arteries  or  veins,  is  not  at  all  or  but  slightly  mixed  with  blood,  is 
confined  in  vessels  of  regular  calibre  with  closed  walls,  and  consequently 
has  not  those  irregular  outlines  characteristic  of  injections  in  hemal 
nodes.  Moreover,  vascular  injections  of  the  lymphatic  nodes  always 
show  a  very  characteristic  arborization,  (fig.  9),  the  distribution  of  the 
injection  mass  throughout  the  specimen  is  quite  uniform,  and  the  capsule 
is  rarely  also  surrounded  by  a  network  of  fine  injected  capillaries,  a  ver- 
itable retia  mirabilia.  It  should  be  mentioned  in  this  connection,  how- 
ever, that  Weidenreich  [37]  stated  that  the  vein,  and  especially  the  artery, 
frequently  branches  as  it  approaches  the  hilus  of  hemolymph  nodes,  send- 
ing branches  to  the  capsule  and  thus  giving  the  whole  a  very  artistic  ap- 
pearance, which  may  cause  confusion  in  embryonic  nodes. 

These  differences  in  the  behavior  of  hemal  and  lymphatic  nodes  upon 
injection  can  easily  be  accounted  for,  it  seems  to  me:  for  in  the  lymph 
nodes  the  injection  mass  merely  has  to  penetrate  permanent  channels  of 
gradually  changing  calibre,  lined  throughout  by  endothelium  and  sur- 
rounded by  tissue,  which  can  easily  yield ,  because  the  lymph  sinuses, 
which  form  a  comparatively  large  portion  of  the  total  volume  of  the  node, 
are  easily  compressible.  In  hemal  nodes,  on  the  contrary,  the  injection 
mass,  instead  of  traversing  a  closed  permanent  system,  must  apparently 
traverse  very  irregular,  often  collapsed,  and  no  doubt  to  a  certain  extent 
discontinuous  because  evanescent,  channels  of  greatly  varying  calibre, 
which  often  have  but  minute  inter-communications,  and  which  also  com- 
municate indirectly  with  the  blood  spaces  of  the  node.  It  is  obvious,  to 
be  sure,  that  improvements  in  technique  may  invalidate  some  of  these 
statements ,  but  they  are  in  harmony  with  results  obtained  with  all  solu- 
tions, suspensions  and  masses  used  in  the  present  series  of  experiments. 

Although  the  artery  and  vein  generally  enter  the  node  together,  in 
external  form  the  hemal  nodes  of  the  sheep  are  usually  oval  or  spheroid- 
al, and,  as  previously  stated,  without  a  definite  hilus.  It  is  true  that  the 
larger  nodes  generally  have  a  more  definite  hilus ,  but  accessory  veins 
usually  do  not  have  accessory  hiluses.  After  piercing  the  capsule,  the 
artery  and  vein  generally  part  company  at  once,  and  only  exceptionally 
traverse  the  substance  of  the  node  as  contiguous  structures.  (Fig.  10.) 


LYMPHATIC    AND    VASCULAR    RELATIONS  27 

The  artery  branches  frequently,  as  it  penetrates  deeper  into  the  node, 
the  smallest  branches  usually  being  found  easiest  near  the  periphery. 
Although  the  arteries  can  only  rarely  be  seen  opening  directly  into 
venous  lacunae,  they  can  frequently  be  seen  in  the  lymphatic  tissue  near 
them.  Since  the  smallest  arteries,  arterioles,  and  the  capillaries  are  prac- 
tically always  empty  and  collapsed,  identification  of  the  capillaries  is 
necessarily  difficult.  Rarely  an  artery  can  be  seen  to  traverse  a  small 
node,  branching  as  it  does  so,  and  leaving  the  node  approximately  oppo- 
site to  the  point  at  which  it  entered,  with  apparently  the  same  calibre. 
(Fig.  n.)  It  is  evident  that  such  variations  of  the  vascular  system  of 
the  node  as  these  can  also  easily  account  for  a  number  of  anomalous  re- 
sults obtained  in  the  course  of  injections. 

Immediately  after  piercing  the  capsule  the  veins,  on  the  other  hand, 
often  communicate  by  means  of  very  wide  openings  directly  with  the  ex- 
tensive venous  lacunae  which  lie  parallel  to  the  peripheral  (sinus)  blood 
space,  when  present,  near  the  outer  border  of  the  lymphatic  tissue;  but 
they  can  only  rarely  be  seen  to  communicate  with  the  subcapsular  or 
central  or  internal  blood  spaces  of  the  parenchyma.  (Figs.  8  and  10.) 
Less  frequently  they  can  also  be  seen  to  communicate  directly  with  the 
deeper-seated  lacunae,  and  with  large  blood  spaces  in  depleted  nodes. 
Accessory  veins,  which  were  clearly  tributary  to  the  peripheral  (sinus) 
or  subcapsular  blood  space,  and  hence  affluent  veins,  were  occasionally 
found,  however.  (Fig.  12.)  In  some  nodes,  on  the  contrary,  it  was 
impossible  to  detect  the  presence  of  a  single  vein  or  venule  within  the 
node  itself,  although  serial  sections  were  made.  This  was  found  to  be 
the  case  even  when  numerous  sections  of  arteries  and  arterioles  could  be 
found.  This  fact,  and  the  entire  absence  of  injected  veins  within  some 
nodes,  can  be  accounted  for  by  the  fact  that  in  some  cases  the  veins  ap- 
parently come  into  relation  with  the  peripheral  venous  lacunae  only. 
Consequently,  in  the  absence  of  the  peripheral  (sinus)  blood  space  they 
can  be  seen  only  where  they  pierce  the  capsule.  Moreover,  in  some  cases 
the  trunk  of  the  vein  does  not  pierce  the  capsule  at  all,  but  merely  comes 
into  contact  with  it  in  such  a  way  that  communication  with  the  intra- 
nodal  circulation  is  effected  by  means  of  an  opening  in  the  adjacent  wall 
of  the  vein,  the  node  appearing  to  be  sessile  upon  the  vessel.  Since  no 
separate  vascular  trunk  exists  between  the  node  and  the  tangent  vein 
in  these  instances,  the  near  wall  of  the  latter  might  be  thought  of  as  be- 
ing continued  through  the  capsule,  and  forming  its  venous  circulation. 
As  in  case  of  the  artery,  however,  so  the  vein  in  rare  instances  may  run 
nearly  through  the  center  of  the  node,  communicating  directly  with  the 


28  HEMOLYMPH    NODES    OF    THE    SHEEP 

venous  lacunae  as  it  penetrates  deeper  and  deeper  into  the  lymphatic 
tissue,  apparently  without  the  intervention  of  venules  or  capillaries. 

The  above  considerations  and  observations  seem  to  indicate  quite 
clearly  that  the  blood  which  enters  a  hemal  .node,  wholly  devoid  of  blood 
islands  and  a  peripheral  (sinus)  or  subcapsular  blood  space,  through 
the  artery,  passes  through  arterioles  and  capillaries  directly  into  the 
venous  lacunae  or  true  sinuses.  From  here  it  may,  in  some  cases  at  least, 
at  once  enter  the  larger  central  venous  spaces,  if  present,  and  hence  pass 
directly  to  the  vein ;  or  it  may  in  the  absence  of  a  main  intra-nodal  vein 
enter  the  efferent  vein  directly  from  the  lacunae.  Since  in  the  above 
case  the  absence  of  blood  islands  and  blood  spaces  has  been  assumed,  the 
relation  of  these  structures  to  the  circulatory  conditions  will  be  consid- 
ered farther  on.  Consequently  the  only  thing  open  to  question  in  the 
above  premises  is  the  manner  of  termination  of  the  arteries,  their  rela- 
tion to  the  blood  spaces  or  areas  when  present,  and  to  venous  lacunae, 
and  the  relation  of  the  latter  to  the  vein.  That  the  arteries  end  in  capil- 
laries, is  easy  to  demonstrate ;  but  it  is  very  difficult  to  demonstrate  satis- 
factorily that  these  capillaries  communicate  directly  with  the  venous 
lacunae,  except  experimentally.  The  presence  in  arterial  injections  of 
the  injection  mass  in  the  lacunae  is,  of  course,  alone  sufficient  evidence 
to  establish  a  direct  connection  between  the  latter  and  arteries ;  but  it 
must  be  admitted  that  the  actual  demonstration  of  a  direct  continuation 
of  an  injected  capillary  into  an  injected  lacuna  is  only  very  occasionally 
possible.  This  fact  may,  to  be  sure,  be  accounted  for  by  the  contractil- 
ity of  the  small  arterial  endings,  and  especially  by  shrinkage  of  the  node, 
as  a  result  of  which  the  injection  material  contained  in  the  fine  arteries 
is  forced  out  into  the  relatively  very  much  larger  venous  lacunae.  The 
direct  communication  of  the  lacunae  with  the  larger  venous  spaces,  or 
with  the  veins,  can,  however,  be  seen  easily,  and  can  be  demonstrated 
satisfactorily  in  both  injected  and  non-injected  specimens,  even  in  the 
case  of  some  very  depleted  nodes.  Since  the  lacunae  form  a  venous 
plexus  of  widely  varying  calibre,  which  must  usually  be  many  times  the 
volume  of  the  arterial  tree,  a  decided  disproportion  between  the  size  and 
volume  of  a  capillary  and  the  lacunae  into  which  it  empties  naturally 
exists.  Consequently  it  is  evident  that  a  decided  slowing  of  the  blood 
current  must  also  take  place  here. 

Although  all  attempts  to  demonstrate  the  existence  of  an  endothelial 
lining  in  the  lacunae  by  means  of  silver  stains  have  so  far  been  futile, 
it  cannot  be  doubted  from  microscopical  examination  of  the  ordinary 
specimens  alone  that  such  an  endothelium  exists.  For,  except  at  points 


LYMPHATIC    AND    VASCULAR    RELATIONS  2H) 

here  and  there  where  small  gaps  are  found,  the  injection  mass  of  India 
ink  is  always  retained  by  a  very  definite  wall.  The  existence  of  discon- 
tinuities in  the  walls  of  the  lacunae  can,  however,  also  be  demonstrated 
microscopically,  and  is  further  proven  by  the  escape  of  some  of  the  in- 
jected pigment  or  gelatine  mass  into  the  surrounding  lymphatic  tissue  in 
specimens  in  which  extravasations  can  be  excluded  because  they  were 
injected  under  conditions  of  a  free  outflow.  This  is  true  no  matter  how 
carefully  the  injection  has  been  made.  In  many  places  a  communication 
of  the  lacunae  with  the  surrounding  parenchyma  is  further  suggested  by 
the  arrangement  of  the  lymphocytes  and  erythrocytes  in  portions  of 
empty  or  partially  empty  lacunae.  In  some  instances  a  number  of  lym- 
phocytes and  blood  corpuscles  are  so  arranged  as  to  suggest  that  they 
are  entering  the  lacunae  from  the  parenchyma.  The  peculiar  disposition 
of  these  cells  may  be  a  purely  accidental  one,  to  be  sure;  but  the  com- 
parative frequency  of  these  very  suggestive  cellular  arrangements  would 
seem  to  imply  that  this  is  not  the  case.  If  these  appearances  were  due 
to  damage  done  to  the  specimens,  it  would  be  impossible  to  explain  why 
the  walls  of  the  lacunae  always  curve  gently  outward  and  disappear 
among  the  surrounding  lymphocytes,  rather  than  ending  abruptly  and 
projecting  into  the  interior  of  the  lacunae  and  giving  the  appearance  of 
torn  ends.  Moreover,  there  is  nothing  in  the  distribution  of  the  pigment 
that  suggests  an  explosive  rupture,  such  as  is  frequently  seen  in  case  of 
extravasations. 

It  is  to  be  remembered  in  this  connection,  to  be  sure,  that  since  con- 
siderable quantities  of  erythrocytes  are  frequently  found  in  the  paren- 
chyma and  sinuses  of  lymph  nodes,  these  must  have  penetrated  not  only 
the  walls  of  the  blood  vessel  but  those  of  the  lymph  sinuses  as  well, 
in  so  far  as  they  did  not  enter  the  latter  through  the  afferent  lymphatics. 
However,  there  is  a  marked  difference  in  appearance  of  the  parenchyma 
of  hemorrhagic  lymph  nodes  and  typical  hemal  nodes ;  and  no  matter 
how  the  presence  of  erythrocytes  in  lymph  nodes  may  be  explained,  it 
seems  highly  improbable  to  me  that  their  presence  in  hemal  nodes  can 
be  similarly  explained.  Helly  concluded  that  hemorrhages  are  respon- 
sible for  red  lymph  nodes,  while  v  Schumacher  reiterated  with  increas- 
ing emphasis  that  in  both  hemorrhagic  lymph  nodes  and  hemal  nodes 
the  erythrocytes  likely  enter  the  sinuses  and  the  parenchyma  through 
places  in  the  walls  of  veins  and  capillaries  which  have  been  weakened  by 
the  passage  of  lymphocytes.  Neuman  thought  the  walls  were  weakened 
by  disease,  v  Schumacher  also  explained  the  presence  of  extravasations 
of  injection  mass  in  the  parenchyma  of  lymph  and  hemal  nodes  in  this 


30  HEMOLYMPH    NODES    OF    THE    SHEEP 

way,  and  concluded  that  the  vascular  system  of  hemal  nodes,  i.  e.,  of 
nodes  having  no  lymphatics  and  containing  much  blood,  is  a  closed  sys- 
tem, as  is  the  case  in  lymph  nodes,  v  Schumacher  based  this  conclusion 
on  the  fact  that  the  injection  mass  by  no  means  always  enters  the  paren- 
chyma of  hemal  nodes,  and  that  it  occasionally  does  so  in  lymph  nodes. 
Hence  he  rules  out  all  the  instances  where  injection  mass  is  found  outside 
of  the  circulation ,  but  only  denies  the  existence  of  a  regular  communica- 
tion between  the  blood  vessels  and  blood  spaces.. 

Attention  was  called  to  the  fact  that  there  is  a  decided  difference  in 
the  frequency  and  nature  of  these  extravasations  in  hemal  nodes,  and 
that  microscopical  evidence  of  the  communication  between  the  venous 
sinuses  or  radicles  and  the  parenchyma  is  not  wanting.  Hence,  in  short, 
the  circulation  of  hemal  nodes  is  similar  to  that  of  the  spleen,  and  not 
to  that  of  lymph  nodes.  I  cannot  believe  that  the  openings  in  the  venous 
sinuses  are  purely  accidental,  or  that  all  the  erythrocytes  entered  the  par- 
enchyma of  hemal  nodes  at  places  which  lymphocytes  had  previously 
weakened.  Moreover,  I  fully  agree  with  Weidenreich  in  regarding  the 
spleen  as  only  a  higher  ( ?)  type  of  hemal  gland.  Schmalz,  too,  thought 
hemal  glands  may  be  designated  accessory  spleens. 

Since  it  has  been  entirely  impossible  to  demonstrate  a  direct  com- 
munication between  the  arteries  and  the  blood  islands  or  spaces,  it  ap- 
pears to  me  that  these  communications  between  the  lacunae  and  the  par- 
enchyma must  be  regarded  as  affording  the  only  means  of  entrance  of 
the  leucocytes  of  the  node  into  the  circulation ;  except,  of  course,  by  pas- 
sage through  the  wall,  as  in  lymph  nodes,  and  through  a  free  communica- 
tion between  the  peripheral  blood  spaces  and  the  veins,  which  occasional- 
ly exists  in  depleted  .nodes.  That  this  statement  necessarily  needs  modifi- 
cation to  suit  the  conditions  existing  in  seriously  depleted  nodes,  is  evi- 
dent, of  course.  Furthermore,  the  fact  that  the  blood  spaces — blood 
islands  including  the  peripheral  blood  space — always  contain  reticulum 
and  have  no  bounding  wall,  while  the  venous  lacunae  and  venous  spaces 
never  contain  reticulum  but  always  have  a  definite  wall,  also  seems  to 
imply  that  the  latter  represent  definite  permanent  channels  whose  endo- 
thelium  cannot  well  be  co-extensive  with  the  reticulum,  and  which  are 
in  direct  relation  with  the  veins.  Hence  the  conclusion  that  all  the 
lymphatic  tissue  and  the  included  blood  islands  and  blood  spaces  lie 
wholly  outside  the  continuous  circulatory  system  as  a  rule,  seems  entirely 
justified.  But,  whatever  the  relation  of  these  structures  to  the  circula- 
tion of  hemal  nodes,  being  inconstant  and  transient,  they  manifestly 
cannot  be  regarded  as  forming  an  integral  part  of  a  system  of  con- 


LYMPHATIC    AND   VASCULAR   RELATIONS  3! 

tinuous  endothelium-lined  channels.  The  so-called  venous  sinuses,  i.  e., 
the  subcapsular  or  peripheral  'blood  space  as  well  as  the  central  or  in- 
ternal blood  spaces,  are,  on  the  contrary,  not  bounded  by  a  definite  wall, 
and  their  contents  are  directly  continuous  with  the  parenchyma  of  the 
rest  of  the  node,  v  Schumacher  too  called  attention  to  this  fact,  and  be- 
lieves that  the  wall  of  the  sub-capsular  blood  space,  which  he  regards 
as  having  been  a  true  marginal  lymph  sinus  developmentally,  was  proba- 
bly incomplete  from  the  beginning.  Consequently  then,  these  fluctuating 
vascular  areas  could  be  regarded  as  spaces  resulting  wholly  or  in  part 
from  a  depletion  of  the  parenchyma  of  the  node,  with  subsequent  or, 
perhaps  better,  simultaneous  substitution  of  blood  cells.  Hence  these 
areas  can  continue  to  exist  only  as  long  as  the  withdrawal  of  lymphocytes 
from  the  node  into  the  circulating  blood  exceeds  their  proliferation 
within  the  node.  Moreover,  if  the  existence  of  a  definite  endothelium 
continuous  with  that  of  the  lacunae  would  have  to  be  assumed  for  the 
central  and  peripheral  blood  spaces,  then  it  would  be  difficult  indeed  to 
explain  why  the  blood  corpuscles  are  frequently  distributed  quite  uni- 
formly among  the  lymphocytes  throughout  the  whole  node,  and  how 
such  endothelial  walls  could  so  rapidly  accommodate  themselves  to  the 
comparatively  rapid  and  very  extensive  fluctuations  in  size  which  they 
would  be  compelled  to  undergo  in  response  to  increase  or  decrease  of 
the  hemal  areas.  Furthermore,  it  would  be  still  more  difficult  to  explain 
why  the  injection  masses  become  distributed  irregularly  in  all  directions 
among  the  cells  of  the  parenchyma  as  soon  as  they  pass  out  of  the  lacu- 
nae, and  why  the  vein  draining  a  node  can  never  be  shown  to  open  directly 
into  the  subcapular  blood  space  at  the  periphery,  and  can  only  rarely  be 
shown  to  communicate  indirectly  with  it  through  the  intervention  of 
blood  spaces  or  blood  islands  in  the  interior.  Such  a  supposition  would 
require  that  the  peripheral  and  central  blood  spaces  must  be  thought  of 
as  extensive  dilations  which  are  practically  coextensive  in  many  cases  with 
the  node  itself,  and  which  communicate  with  the  lacunae  by  very  nar- 
row channels.  It  would  then  also  be  necessary  for  all  the  lymphocytes 
to  pass  through  this  wall  of  endothelium  before  they  could  enter  the  cir- 
culation;  and,  on  the  other  hand,  the  blood  corpuscles  would  likewise 
have  to  penetrate  the  same  wall  upon  entrance  to  and  exit  from  the  par- 
enchyma of  the  node;  and  the  only  alternative  to  this  assumption  is  that 
both  arteries  and  veins  end  freely  in  the  parenchyma — for  which  I  can 
find  no  evidence.  I  fully  realize  that  the  circulatory  conditions  as  as- 
sumed above  supply  no  reason  for  the  migration  of  lymphocytes  into  the 
blood,  and  that  they  do  not  account  for  the  occurrence  of  gaps  in  the 
walls  of  the  lacunae.  Yet  the  conclusions  reached  are  no  more  invali- 


32  HEMOLYMPH    NODES    OF    THE    SHEEP 

dated  by  these  considerations  than  the  current  and  more  or  less  accepted 
statement  regarding  the  circulatory  conditions  in  the  spleen  is  invalidated 
by  similar  considerations.  To  be  sure,  a  purely  mechanical  explanation  is 
not  suggested  as  adequate  or  final ;  but  since  this  conception  not  only 
harmonizes  with  the  observed  facts  but  quite  satisfactorily  accounts  for 
most  of  the  difficulties,  it  seemed  justified. 

In  the  assumed  case,  then,  in  which  practically  all  of  the  node  is 
formed  by  a  mass  of  lymphatic  tissue  containing  a  few  blood  cells,  the 
supposition  would  be  that  there  is  a  very  slow  movement  of  lymphocytes 
from  the  parenchyma  into  the  blood  stream,  and  a  correspondingly  slow, 
though  not  necessarily  a  purely  passive  movement  of  the  blood  cells  in 
the  opposite  direction.  Wherever  local  depletion  of  the  parenchyma 
occurred  blood  islands  and  blood  spaces  would  naturally  form;  and 
whenever  a  more  or  less  general  or  local  depletion  of  lymphatic  tissue 
took  place  along  the  periphery  of  the  node,  a  continuous  or  discontinu- 
ous peripheral  blood  space  could  also  result.  It  is,  of  course,  also  prob- 
able that  the  accessory  affluent  veins  sometimes  present,  may  be  in  part 
responsible  for  the  formation  and  persistence  of  a  more  or  less  continu- 
ous peripheral  blood  space,  and  that  rapid  depletion  of  the  lymphatic 
tissue  of  the  node  might  result  in  decreasing  the  size  of  the  node.  How- 
ever, since  it  is  unlikely  that  the  capsule  and  framework  of  the  node  can 
accommodate  themselves  rapidly  to  the  altered  conditions,  an  opportunity 
would  be  afforded  for  blood  to  occupy  the  depleted  periphery  and  so 
form  a  peripheral  blood  space.  Since  the  lymphocytes  must  be  carried 
away  by  the  blood  stream,  they  would  of  course  have  a  tendency  to 
gather  about  the  venous  ostia  of  the  lacunae,  thus  explaining  the  occur- 
rence of  remnants  of  the  lymphatic  tissue  about  empty  lacunae  and  near 
the  periphery  in  depleted  nodes,  although  it  is  unlikely  that  a  purely  me- 
chanical explanation  is  adequate.  In  depleted  nodes  the  more  or  less  stag- 
nant blood  may  then  undergo  degenerative  changes ;  and,  since  the  frag- 
ments of  the  erythrocytes  can  probably  pass  out  easier  with  the  lympho- 
cytes than  the  intact  cells,  the  presence  of  granular  deposits  in  the  lacunae 
would  also  be  accounted  for.  If,  in  addition,  it  be  recalled  that  some  of 
the  openings  into  the  lacunae  are  undoubtedly  obstructed  partly  or 
wholly  by  collapse  of  their  walls  through  encroachment  of  the  lymphatic 
tissue,  the  correctness  of  the  above  supposition  regarding  the  post-em- 
bryonic genesis  of  such  inconstant  and  transient  structures  as  the  blood 
spaces  and  blood  islands  is  made  still  more  probable. 

It  is  interesting  to  recall  in  this  connection  that  Weidenreich  [37] 
considered  the  blood  as  passing  through  the  parenchyma  between  the 
blood  spaces  and  lacunae  under  ordinary  conditions,  but  assumed  that 


LYMPHATIC    AND   VASCULAR    RELATIONS  33 

under  extraordinary  circumstances  it  traversed  a  system  of  arterioles 
which  form  a  direct  passage  between  the  blood  spaces  and  the  lacunae, 
and  which  he  regarded  as  playing  the  role  of  a  self-regulatory  system. 
According  to  this  conception,  for  example,  if  for  some  reason  the  pres- 
sure within  the  node  becomes  too  high,  this  system  of  arterioles  is  sup- 
posed to  be  thrown  open  automatically  until  conditions  of  normal,  or  at 
least  of  a  reduced  pressure,  again  obtain.  Even  granting  the  existence  of 
such  a  self-regulatory  system,  I  have  been  unable  to  confirm  either  the 
occurrence  of  arterioles  uniting  blood  spaces  and  venous  lacunae,  or  the 
occurrence  of  the  thickenings  in  the  walls  of  capillaries  by  means  of  which 
this  regulatory  function  is  supposed  to  be  effected.  Moreover,  it  is  more 
than  likely  that  if  such  connecting  arterioles  existed  in  any  number  one 
might  reasonably  expect  the  blood  spaces  and  these  arterioles,  rather  than 
the  lymphatic  tissue  between  lacunae  and  blood  spaces,  to  become  injected. 
This  is,  however,  not  the  case. 

If  the  calibre  of  an  artery  supplying  a  node  is  compared  with  the 
area  of  the  mtra-nbdal  venous  system,  it  is  evident  that  the  intra-venous 
circulation  must  of  necessity  be  a  very  sluggish  one,  although  increases 
in  pressure  might  nevertheless  slightly  accelerate  the  intra-nodal  cur- 
rent. This  would  of  course  be  true,  even  if  not  nearly  to  the  same  ex- 
tent, whether  the  circulation  is  a  closed  or  an  open  one.  This  supposed 
sluggishness  of  the  current  is  confirmed  by  the  results  of  injections  from 
the  aorta,  for  it  will  be  recalled  that  small  lymph  nodes  manifested  color 
changes  almost  instantly,  and  that  the  finest  capillaries  were  later  found 
to  contain  injection  mass,  while  many  of  the  hemal  nodes  remained  unin- 
jected,  and  only  a  few  manifested  slight  color  changes.  Consequently 
it  seems  to  me  that  if  arterioles  connected  the  blood  spaces  and  venous 
lacunae,  one  might  reasonably  expect  them  to  become  injected,  even  if 
not  as  readily  as  the  capillaries  in  lymph  nodes.  Besides,  if  the  arterial 
capillaries  opened  directly  into  the  parenchyma,  or  if  other  than  indirect 
communications  between  the  blood  spaces  and  lacunae  existed,  it  would 
be  difficult  indeed  to  explain  why  blood  should  accumulate  within  the 
node,  as  it  usually  does.  It  is  also  evident  that  if  the  disposition  of  the 
vascular  circulation  in  hemal  nodes  were  comparable  to  the  lymphatic 
circulation  in  lymph  nodes,  it  should  not  be  so  exceedingly  difficult  to 
inject  hemal  nodes  from  the  aorta ;  for  the  ease  with  which  lymph  nodes 
can  be  injected  from  the  periphery,  and  the  speed  with  which  they  man- 
ifest color  changes  are,  of  course,  striking.  Hence  it  seems  to  me  that 
these  considerations  alone  suffice  to  establish  the  fact  that  the  relation  of 
the  peripheral  and  central  blood  spaces  to  the  veins  of  hemal  nodes  must 
be  essentially  different  from  that  of  the  lymphatic  vessel  to  the  peripheral 
and  central  sinuses  of  lymph  nodes. 


34  HEMOLYMPH    NODES    OF    THE    SHEEP 

THE  MICROSCOPIC  STRUCTURE 

Under  low-power  magnification  a  hemal  node  in  section  may  show 
nothing  but  a  thin  capsule  containing  a  solid  mass  of  lymphoid  tissue 
with  few  or  no  follicles  or  trabeculae,  and  with  but  a  sprinkling  of  barely 
noticeable  erythrocytes.  Or,  on  the  other  hand,  it  may  look  like  a  sac 
filled  with  blood  in  which  the  coarser  framework  of  the  node  is  revealed 
here  and  there,  but  with  only  a  few  small  masses  of  lymphoid  tissue  with 
or  without  lacunae  containing  some  blood  cells  and  granular  detritus. 
In  short,  then,  the  appearance  of  a  hemal  node  on  section  may  be  similar 
to  that  of  a  section  of  sheep's  spleen  without  Malphighian  corpuscles  and 
few  erythrocytes  and  but  few  and  small  trabeculae,  on  the  one  hand ;  or 
that  of  a  sack  of  blood  containing  a  few  small  islands,  or  merely  scat- 
tered lymphocytes  or  groups  of  them  lying  near  small  connective  tissue 
trabeculae,  on  the  other.  Rarely,  too,  one  finds  a  practically  empty  node 
containing  but  little  lymphatic  tissue  surrounded  by  scattered  erythrocytes 
and  enclosing  wide-open  spaces ;  the  venous  lacunae  of  Weidenreich,  con- 
taining some  granular  detritus  and  degenerated  blood  corpuscles.  Be- 
tween these  extremes  literally  every  conceivable  gradation  is  found.  The 
cross-section,  for  example,  may  be  crowded  with  follicles  (figs.  6  and  14) 
which  encroach  on  each  other,  on  the  blood  islands,  and  even  on  the  per- 
ipheral (sinus)  blood  space;  or,  perchance,  they  may  be  absent  alto- 
gether (fig.  15).  A  classification  of  follicles  into  definite  types,  as  reported 
by  Vincent  and  Harrison  [28],  was  never  possible;  and  such  differences 
as  were  observed  were  structurally  of  a  very  minor  character.  A  like 
inconstancy  is  found  in  case  of  the  empty  venous  lacunae  found  in  the  par- 
enchyma, which  are  frequently  very  conspicuous  in  nodes  containing  much 
blood  but  little  lymphatic  tissue.  (See  figs.  16  and  17.)  It  is  these 
spaces,  I  take  it,  which  have  probably  been  mistaken  for  lymph  spaces. 

Equally  great  variations  exist  in  all  the  constituents  of  hemal  nodes, 
save  perhaps  the  capsule  and  the  artery.  These  are  the  least  subject  to 
variations ;  although  it  is  evident  that  in  a  node  which  practically  repre- 
sents a  sac  of  blood  the  original  distribution  and  disposition  of  the  artery 
must  also  have  been  modified  very  profoundly.  It  follows,  to  be  sure, 
from  these  considerations  that  a  node  having  neither  blood  islands  nor 
blood  spaces,  not  even  a  peripheral  (sinus)  blood  space  or  evident  venous 
lacunae,  may  yet  be  a  true  hemal  node.  And,  on  the  contrary,  it  also 
follows  that  a  node  containing  a  mere  remnant  of  lymphatic  tissue  in  a 
mass  of  blood  may  also  be  a  true  hemal  node  (figs.  18  and  19).  This 
being  the  case,  it  is  highly  probable  that  these  facts  account  in  some  meas- 
ure at  least  for  the  confusion  regarding  the  occurrence  of  mixed  nodes,. 


MICROSCOPIC   STRUCTURE  35 

and  possibly  also  for  the  contention  that  a  transformation  occurs  from 
hemal  to  lymph  nodes,  and  vice  versa.  For,  as  already  stated,  such  a 
transformation  might  well  be  assumed  to  occur,  because  an  actual  series 
of  nodes  with  but  slight  structural  differences — except  circulatory — be- 
tween the  successive  nodes,  can  be  formed  with  true  hemal  and  lymph 
nodes,  as  extremes.  In  such  a  series  it  would  be  entirely  impossible  to 
differentiate  many  of  the  intermediate  nodes  from  external  appearances, 
or  by  a  cursory  microscopic  examination ;  and  it  should  be  remembered 
that  injection  methods  alone  made  positive  identification  possible  in 
many  cases  of  these  apparently  transitional  forms. 

In  those  nodes  in  which  the  blood  corpuscles  were  not  intermingled 
more  or  less  uniformly  with  the  parenchyma,  they  formed  masses  which 
contained  some  lymphocytes,  especially  at  the  periphery  of  the  masses. 
These  local  accumulations  of  blood-cells — blood  islands — vary  in  size 
from  small  groups  of  cells  to  larger  masses  which  may  compose  the 
greater  part  of  the  area  of  the  node.  There  are  nodes,  for  example,  con- 
taining a  single  blood  island  practically  co-extensive  with  the  node,  and 
forming  perhaps  nine-tenths  or  more  of  the  area  of  the  section  (figs.  15, 
18  and  19).  Others,  on  the  contrary,  may  contain  hundreds  of  minute 
blood  islands  which  may  nevertheless  form  but  an  insignificant  fraction 
of  the  total  volume  of  the  node.  When  small,  numerous  and  isolated 
these  islands  often  give  a  spotted  appearance  to  the  cross-section  under 
low-power  magnification.  If,  on  the  contrary,  they  are  very  large,  they 
are  often  ill-defined,  generally  irregular  in  shape,  and  more  or  less  con- 
tinuous with  each  other,  with  the  blood  in  the  peripheral  blood  space,  and 
with  the  large  central — internal — spaces,  if  present.  A  union  of  the  per- 
ipheral and  more  external  blood  spaces  into  central  collecting  spaces  was 
never  observed. 

It  is  evident,  of  course,  that  a  peripheral  blood  space  can  exist  only 
when  sufficient  lymphatic  tissue  is  preserved ;  for  when  the  latter 
is  greatly  reduced  in  quantity,  all  boundaries  are  completely  ef- 
faced, thus  allowing  the  blood  islands  or  spaces  to  merge.  Hence  as 
more  and  more  of  the  lymphatic  tissue  of  the  node  disappears  and  the 
total  hemal  area  becomes  larger  and  larger,  a  stage  is  finally  reached 
in  which  the  peripheral  and  central  blood  islands  or  spaces  merge  into 
an  area  in  which  only  remnants  of  the  once  predominant  lymphatic  tissue 
are  found.  But  whether  these  blood  islands  in  the  parenchyma  were 
large  or  small,  the  blood  was  only  very  rarely  found  to  be  in  a  state  of 
evident  degeneration,  except  in  nodes  which  were  largely  or  almost 
wholly  devoid  of  lymphatic  tissue. 

The  cellular  content  of  the  blood  islands  did  not  vary  markedly  from 
that  of  the  veins ;  although  at  the  periphery  of  the  islands,  and  especially 


36  HEMOLYMPH    NODES    OF    THE    SHEEP 

at  the  inner  margin  of  the  peripheral  blood  space,  there  were  fewer  poly- 
morphonuclear  leucocytes  and  eosinophiles,  but  more  lymphocytes.  How- 
ever, in  some  of  the  largest  blood  islands,  and  in  nodes  in  which  blood 
had  so  extensively  displaced  the  lymphatic  tissue,  extremely  few  lymph- 
ocytes were  found  among  the  solidly  packed  erythrocytes. 

Eosinophiles  were  present  in  the  hemal  areas  in  small  numbers  only, 
being  confined  almost  entirely  to  the  surrounding  lymphatic  tissue.  In 
the  case  of  very  large  blood  islands  the  intermingling  of  erythrocytes  and 
lymphatic  tissue  was  occasionally  so  extensive,  however,  that  there  were 
approximately  as  many  cells  of  the  one  kind  as  of  the  other.  However, 
in  some  cases  most  of  the  blood  was  found  distributed  rather  evenly 
among  the  lymphoid  tissue.  It  seems  probable  that  this  condition  results 
from  a  secondary  invasion  of  the  blood  spaces  by  the  surrounding  lymph- 
ocytes, rather  than  by  an  invasion  of  the  surrounding  parenchyma  by 
erythrocytes,  although,  to  be  sure,  primarily  the  lymphatic  tissue  was 
displaced  by  blood  cells.  No  matter  what  the  character  of  a  node,  the 
boundaries  between  the  blood  islands  and  lymphoid  tissues  were  ill- 
defined,  as  a  rule  (see  fig1.  20).  Occasionally,  however,  a  well-defined 
wall,  of  rather  coarse  reticulum,  was  present  between  the  two  (fig.  21  ). 
This  bounding  reticulum  between  blood  islands  and  lymphatic  tissue 
was  seldom  very  apparent,  except  in  a  few  nodes  which  contained  so  little 
blood  and  lymphatic  tissue  that  they  were  practically  empty.  In  these 
nodes  the  lymphatic  tissue  had  been  reduced  to  such  an  extent  that  one 
might  rightly  speak  of  islands  of  lymphatic  tissue  in  a  hemal  area.  As 
might  be  expected,  however,  there  seemed  to  be  very  little  intermingling 
of  the  blood  and  lymphocytes  in  by  far  the  greater  portion  of  some  of 
these  nodes.  Moreover,  since  these  walls  of  reticulum  are  often  similar 
or  identical  to  the  walls  of  the  apparently  condensed  reticulum  seen  at 
the  periphery  of  a  follicle,  it  is  possible  that  the  accumulation  of  blood 
in  the  empty  reticulum  may  be  an  important  factor  in  producing  them. 
This  supposition  seems  to  be  supported  by  the  fact  that  they  were  seldom 
or  only  partially  present,  around  very  small  blood  islands.  Moreover, 
whenever  the  total  amount  of  blood  was  larger  the  contiguous  surfaces 
of  blood  and  lymphatic  tissue  were  often  indicated  by  a  gently  curving 
line,  instead  of  by  a  very  irregular  and  ill-defined  one.  However,  here  and 
there  a  portion  of  lymphatic  tissue  of  irregular  form  might  nevertheless 
extend  boldly  out  into  the  surrounding  blood.  It  is  only  occasionally 
that  blood  islands  are  found  within  the  follicles;  and  when  so  found  they 
are  generally  small,  and  never  seem  to  be  continuous  with  those  outside 
of  them.  Nevertheless  their  absence  rather  than  their  presence  here 
would  seem  to  need  an  explanation. 


MICROSCOPIC   STRUCTURE  37 

In  addition  to  the  large  venous  spaces  in  direct  communication  with 
the  vein,  usually  located  near  the  center  of  the  node,  when  present,  there 
are  small  and  more  numerous  ones,  termed  venous  lacunae  by  Weiden- 
reich  [37].  These  dilated  empty,  or  nearly  empty,  spaces  are  apparently 
most  numerous  and  conspicuous  in  nodes  which  contain  much  more  blood 
than  lymphatic  tissue  (figs.  17  and  19).  Indeed  in  such  nodes  they  are 
frequently  so  numerous,  so  large,  and  so  devoid  of  celluar  content  that 
they  may  give  an  almost  fenestrated  appearance  to  a  section.  In  these 
specimens — and  in  general,  for  that  matter — they  are  most  evident  near 
the  periphery  (figs.  8  and  n).  In  depleted  nodes  this  fact  can,  to  be  sure, 
be  easily  accounted  for  by  the  fact  that  most  of  the  remnants  of  the  lym- 
phatic tissue  are  for  some  reason  found  in  this  location  (fig.  18)  ;  but  why 
they  should  be  more  evident  here  than  elsewhere  in  the  more  typical  nodes 
(fig.  8)  is  not  so  obvious.  Although  the  configuration  of  these  lacunae  or 
true  venous  sinuses  is  an  extremely  irregular  one,  and  although  their  boun- 
daries are  not  always  well  defined,  it  was  nevertheless  quite  often  possible 
to  pass  from  one  lacuna  to  another,  along  almost  the  whole  circumference 
of  a  section  of  uninjected  nodes.  If,  however,  they  were  small,  their  com- 
munication, and  in  fact  their  continuity  with  other  lacunae,  was  not  so 
evident,  although  such  communications  and  continuity  undoubtedly 
existed.  This  apparent  absence  of  inter-communications  between  lacu- 
nae can  probably  be  explained  by  the  fact  that  when  the  walls  of  the  lacu- 
nae are  in  contact  it  is  very  difficult  indeed,  or  impossible  even,  to  dis- 
tinguish the  latter  from  apposed  reticulum  fibers.  Nor  does  the  fact  that 
no  lacunae  whatever  were  visible  in  sections  of  some  nodes  which  had  the 
appearance  of  splenic  tissue,  for  example,  necessarily  imply  that  none 
existed ;  for  a  hemal  node — other  than  a  completely  depleted  one — without 
lacunae  would  seem  to  be  an  impossibility,  because  of  the  probable  or 
even  necessary  circulatory  conditions  which  their  absence  would  seem  to 
imply.  The  absence  of  lacunae  would  practically  transform  the  vascular 
system.  Moreover,  if  the  results  of  the  many  injections  of  the  venous 
system  of  .nodes  can  be  used  as  a  criterion,  it  is  certain  that  lacunae  are  dis- 
tributed throughout  the  entire  node,  with  the  possible  exception  of  the  fol- 
licles ;  unless,  as  seems  improbable  to  me,  the  occasional  presence  of  India 
ink  in  the  latter  can  be  taken  as  satisfactory  proof  of  their  existence  here. 
Since,  of  course,  the  lacunae  contain  no  reticulum,  they  must,  I  believe, 
be  regarded  as  practically  permanent  structures  which  are  an  integral  part 
of  the  venous  system  and  intermediate  in  position  in  the  circulation. 
Many  of  them  persist  until  the  last  remnants  of  lymphatic  tissue  dis- 
appear (fig.  18).  Moreover,  whatever  their  relation  to  the  arteries,  since 


BIO-AGRICULTURAL  LIBRARY 
UNIVERSITY  OF  CALIFORNIA 
RIVERSIDE,  CALIFORNIA  92502 


38  HEMOLYMPH    NODES    OF    THE    SHEEP 

they  are  usually  empty  save  for  small  amounts  of  granular  material 
(fig.  21 ),  it  is  clear  from  this  and  other  direct  evidences  that  they  com- 
municate rather  freely  with  the  large  central  venous  spaces  and  the  drain- 
ing veins.  That  they  must,  however,  also  communicate  in  some  manner 
with  the  lymphatic  tissue  and  the  blood  islands  and  blood  spaces,  is  indi- 
cated by  such  appearances  as  those  represented  in  fig.  20,  and  by  the 
results  of  many  puncture  injections,  as  well  as  by  other  considerations. 

While,  then,  it  was  comparatively  easy  to  determine  the  direct  con- 
nection between  lacunae  and  veins,  microscopically  alone,  their  relation- 
ship to  arteries  could  be  demonstrated  satisfactorily  only  by  injection 
methods,  for  no  matter  how  close  to  a  lacuna  the  arterial  terminations 
were,  they  were  only  seldom  seen  to  open  directly  into  them  (fig.  23). 
Nor  was  it  easily  possible  to  demonstrate  a  direct  communication  be- 
tween venous  lacunae  and  the  blood  islands  or  blood  spaces  (fig.  24),  or 
between  them  and  the  peripheral  or  subcapsular  blood  space,  except  in 
nodes  whose  structural  relations  had  been  profoundly  altered  as  a  result 
of  decided  depletion  of  the  lymphatic  tissue.  But  even  in  most  of  these 
specimens  a  narrow  and  more  or  less  perfect  barrier  of  lymphatic  tissue 
almost  invariably  separated  them  from  the  blood  islands  or  blood  spaces 
(figs.  13,  21  and  22).  The  existence  of  these  barriers  of  lymphatic 
tissue  between  the  venous  lacunae  and  the  peripheral  blood  space  on  the 
one  hand,  and  the  central  or  internal  blood  spaces  or  blood  islands  on  the 
other,  as  well  as  the  almost  constant  presence  of  an  amorphous  or  slightly 
granular  deposit  in  many  of  them,  even  in  the  case  of  nodes  practically 
devoid  of  lymphatic  tissue,  are  particularly  significant,  it  seems  to  me,  for 
the  elucidation  of  the  somewhat  obscure  circulatory  conditions.  Besides, 
that  the  interpretation  of  these  venous  spaces  or  radicles  as  lymphatic 
spaces,  however  excusable,  is  erroneous,  must  be  evident  from  the  above 
experiments  and  observations. 

In  some  depleted  nodes,  and  very  rarely  also  in  others,  large  con- 
nective tissue  septa  divide  the  node  so  completely  that  the  individual  sub- 
divisions might  almost  be  considered  as  separate  nodes  (fig.  16)  ;  but 
no  specimens  were  found  in  which  the  lymphatic  tissue  could  be  said  to 
be  fibrous  or  muscular,  as  stated  by  Vincent  and  Harrison  [28] .  Indeed, 
in  the  great  majority  of  cases,  there  are  no  evident  septa  or  trabeculae 
extending  inward  from  the  capsule  and  subdividing  the  node.  The 
coarser  reticulum,  however,  is  generally  plainly  visible  in  the  peripheral 
blood  space,  in  many  blood  islands  (fig.  25),  and  throughout  depleted 
nodes,  by  means  of  low  magnification.  That  this  reticulum  is  more  con^ 
spicuous  in  the  peripheral  blood  space  is,  of  course,  due  to  the  fact  that 


MICROSCOPIC   STRUCTURE  39 

it  is  coarser  here  where  it  comes  into  relation  with  the  capsule,  and  be- 
cause it  is  generally  obscured  much  less  here  by  the  presence  of  celluiar 
elements.  In  the  deeper  portions  of  the  node  it  is  much  finer,  denser, 
much  less  cellular,  and  sometimes  not  at  all  apparent  in  the  follicles  in 
sections  stained  in  the  ordinary  way.  The  size  of  the  meshes  of  the  retic- 
ulum  also  vary  markedly  in  different  portions  of  the  node.  They  are 
largest  where  the  fibers  are  coarsest,  and  smallest  where  they  are  of  great- 
est tenuity.  Although  some  very  fine  fibres  can  be  found  in  practically  all 
portions  of  the  parenchyma,  it  is  in  the  follicles  where  the  finest  reticulum 
is  found.  Here  the  meshes  are  often  so  small  in  section  that  they  contain 
but  a  single  cell.  As  in  the  follicles  of  lymph  nodes,  the  reticulum  is  less 
evident  in  the  center,  where  only  an  imperfect  network  can  be  demon- 
strated. Were  this  difference  less  constant  it  might  possibly  be  due  to 
variations  in  staining  power  of  the  reticulum,  or  to  a  faulty  technique ,  but 
the  same  results  were  obtained  by  the  special  stains  used.  Near  the  per- 
iphery of  the  follicle,  on  the  contrary,  the  fibers  seem  crowded  together, 
and  consequently  are  generally  very  evident,  because  they  are  coarser  and 
have  a  rather  circumferential  arrangement.  The  finest  reticulum  fibers 
noticed  were  so  minute  that  they  appeared  as  extremely  fine  lines  under 
the  highest  magnification  used  (x  1340). 

In  the  center  of  many  good-sized  blood  islands,  or  in  blood  spaces, 
reticulum  could  never  be  demonstrated  by  the  Bielschowsky  or  any  other 
method.  Moreover,  in  empty  or  in  partially  empty  nodes  many  of  the 
coarser  reticulum  fibers  in  the  empty  blood  spaces  seemed  to  end  abruptly, 
as  though  they  had  been  forced  asunder.  Nor  was  it  difficult  to  find 
cells  with  six  or  more  processes,  some  of  which  terminated  in  free  ends 
a  short  distance  from  the  cell.  At  the  border  of  large  blood  islands,  or 
of  blood  spaces,  a  very  definite  bounding  or  confining  layer  of  coarse 
reticulum,  from  which  branches  extended  into  the  blood  islands,  was  fre- 
quently present.  In  some  cases  these  walls  of  reticulum  were  formed 
by  several  parallel  fibers,  which  looked  as  though  they  had  been  crowded 
together  more  or  less,  and  which  very  closely  simulated  conditions  found 
at  the  periphery  of  the  follicles.  Were  it  not  for  the  fact  that  this  wall  of 
reticulum  which  separates  the  blood  islands  from  the  lymphatic  tissue  gives 
off  branches  which  are  directly  continuous  with  the  adjacent  reticulum  on 
both  sides,  it  would  be  very  difficult  indeed,  or  impossible  even,  to  distin- 
guish the  walls  of  some  empty  blood  spaces  from  those  of  empty  venous 
lacunae.  However,  generally  only  a  portion  of  the  circumference  of  a  blood 
island  was  thus  bounded,  the  remainder  of  the  boundary  being  formed  by 
the  parenchyma  of  the  node,  in  the  bounding  area  of  which  a  gradual 


4O  HEMOLYMPH    NODES    OF    THE    SHEEP 

change  from  pure  lymphatic  tissue  to  the  blood  contained  in  the  blood 
spaces  could  be  seen.  These  transitional  areas  strikingly  demonstrated 
the  relations  existing  between  blood  islands  or  spaces  and  the  parenchyma 
of  the  node,  and  in  them  it  was  easy  to  see  that  the  blood  in  the  blood 
islands  had  probably  merely  replaced  the  lymphocytes. 

Aside  from  small  quantities  of  plain  muscle  found  near  blood  vessels, 
none  was  observed  save  in  the  capsule,  where  a  few  fibers  could  occasion- 
ally be  distinguished ,  but  these  too  were  probably  associated  with  blood 
vessels.  Hence  the  conclusion  that  involuntary  muscle  is  a  purely  inci- 
dental constituent  of  the  hemal  nodes  of  the  sheep,  seems  justified ;  and 
the  statement  that  hemal  nodes  can  alternately  contract  and  relax,  seems 
a  highly  fanciful  conception,  except  in  so  far  as  such  alternations  in  vol- 
ume may  be  the  result  of  a  varying  pressure  or  fluctuations  in  calibre  of 
the  arteries.  I  am  fully  aware  that  these  observations  are  somewhat  at 
variance  with  those  of  Robertson  [24],  Weidenreich  [37]  and  v  Schu- 
macher [27].  According  to  Weidenreich  unstriated  muscle  and  a  few 
elastic  fibers  are  found,  especially  in  the  inner  layers  of  the  capsule.  Both 
Weidenreich  and  v  Schumacher  state,  however,  that  these  constituents 
vary  greatly  in  amount ;  and  the  former  adds  that  smooth  muscle  was  not 
found  in  the  lymphatic  tissue. 

Although  sections  taken  from  a  number  of  nodes  were  stained  with 
different  elastic  tissue  stains,  undoubted  elastic  tissue  fibers  were  never 
found.  However,  since  all  stains  used  for  this  purpose  also  stain  the 
reticulum  to  some  extent,  it  is  practically  impossible  to  differentiate  these 
two  kinds  of  fibres  definitely  by  the  ordinary  elastic  tissue  stains.  More- 
over, the  fine  reticulum  fibers  which  are  very  numerous  often  branch  and 
have  a  wavy  outline  so  as  to  simulate  elastic  tissue  fibers  very  closely. 
Hence  the  evidence  obtained  in  this  investigation  is  an  entirely  negative 
one  as  far  as  the  occurrence  of  elastic  tissue  is  concerned. 

Neither  could  fat  cells  be  demonstrated  in  the  parenchyma  of  a  num- 
ber of  nodes  examined  after  the  use  of  special  methods  of  fixation  and 
hardening,  such  as  those  of  Vom  Rath,  Flemming,  Herxheimer,  Her- 
mann, or  by  the  use  of  osmic  acid.  Negative  results  were  also  obtained 
with  Herxheimer's  stain  as  modified  by  Bell.  The  only  nodes  in  which 
there  seemed  to  be  a  rather  ill-defined  line  of  demarcation  between  the 
parenchyma  and  the  surrounding  fat  were  developing  nodes,  or  specimens 
in  which  the  generally  inconspicuous  capsule  was  extremely  thin  in  some 
places.  These  observations  regarding  the  relation  of  the  fat,  made  on 
several  hundred  nodes  taken  at  random  from  a  large  series  of  carcasses  of 
sheep,  bovines  and  goats,  stand  in  striking  contrast  to  those  of  Meek  [17] 


MICROSCOPIC  STRUCTURE  4! 

on  nodes  from  three  pigs.  Meek  says  that  "On  microscopical  examina- 
tions they  (the  glands)  are  seen  to  possess  a  very  thin  capsule  and  in 
some  cases  a  distinct  capsule  cannot  be  said  to  exist,  the  peripheral  sinus 
of  the  gland  being  directly  contiguous  with  the  periglandular  fat,  and  the 
cellular  tissue  of  the  sinus  spreading  between  the  contiguous  fat  cells. 
This  condition  much  resembles  that  seen  in  the  marrow  of  the  long  bones 
at  the  junction  of  cellular  and  fatty  marrow."  These  observations  of 
Meek  are  similar  to  those  made  on  sheep  by  Clarkson  [2],  who  stated 
that  the  cells  of  the  surrounding  fat  are  often  in  contact  with  the  adenoid 
tissue.  It  is  particularly  interesting  in  connection  with  Meek's  observa- 
tions that  v  Schumacher  failed  to  find  hemolymph  (hemal)  nodes  in  the 
pig.  Both  he  and  Baum  and  Hille,  who  according  to  v  Schumacher  first 
directed  attention  to  the  matter,  and  also  Baum,  found  fat  cells  bordering 
the  marginal  sinus  in  most  of  the  lymph  nodes  of  the  pig.  Baum  regarded 
this  as  fat  formation  on  part  of  the  reticulum,  beginning  from  the  per- 
iphery and  leading  to  complete  atrophy  of  the  node,  as  due  to  age ;  but  v 
Schumacher  found  that  fat  is  already  present  at  six  months.  The  latter 
also  called  attention  to  the  well-known  fact  that  similar  changes  occur  in 
other  animals,  and  that  erythrocytes  are  normally  present  in  the  lymph 
sinuses  of  lymph  nodes  of  the  pig. 

Intra-capsular  sinuses,  or  blood  spaces,  as  described  by  Robertson 
[24]  as  extending  one-fifth  of  the  distance  around  the  gland,  were  not 
seen ;  although  it  is  not  rare  to  find  free  blood  in  the  looser  portions  of 
the  capsule.  Neither  did  nodes  which  were  almost  depleted  of  lymphatic 
tissue,  and  which  might  perhaps  be  considered  as  undergoing  retrogres- 
sion, show  the  least  sign  of  fatty  degeneration.  However,  Warthin  [33], 
in  writing  of  the  marrow  lymph  nodes  of  man,  reported  the  finding  of 
fat  cells  throughout  this  type  of  node,  and  also  maintained  [34  and  35] 
the  development  of  hemolymph  nodes  from  fat  and  their  degeneration 
into  fat ;  but  Vincent  and  Harrison  [28]  reported  that  "In  no  instance  did 
we  find  any  fat  cells  inside  the  capsule"  in  the  sheep  and  ox. 

The  conclusion  that  the  blood  islands  and  blood  spaces,  both  per- 
ipheral and  central,  are  transient,  and  perhaps  even  quite  incidental 
structures,  seems  amply  justified.  Present  now  and  absent  then,  found  in 
this  node  and  not  in  that,  their  usual  presence  in  developing  nodes  even, 
does  not  signify,  it  seems  to  me,  that  they  are  indispensable  constituents 
of  hemal  nodes.  It  is  not  uncommon,  for  example,  to  find  a  portion  of  a 
node  containing  many  follicles  which  are  in  a  state  of  proliferation,  and 
which  encroach  upon  both  the  peripheral  and  the  central  blood  spaces  or 
blood  islands.  That  such  a  process  must  often  result  in  the  complete  obli- 


42  HEMOLYMPH    NODES    OF    THE    SHEEP 

teration  of  both  peripheral  and  central  blood  spaces  seems  very  likely  in- 
deed. -Moreover,  since  the  blood  spaces  are  usually  engorged  with 
blood,  which  cannot  be  expelled  from  them  by  external  pressure 
even  when  they  are  large,  further  proof  is  given  that  they  probably 
are  not  as  a  rule  in  free  direct  communication  with  the  veins.  For  these 
and  other  reasons,  I  have  come  to  regard  the  blood  islands — the  blood 
spaces  including,  as  a  rule,  the  peripheral  or  subcapsular  blood  space — as 
very  largely  representing  areas  in  which  the  parenchyma  of  the  node  has 
become  depleted  of  lymphocytes,  whose  place  has  either  wholly  or  partly 
been  taken  by  blood.  Since,  however,  this  blood  is  usually  in  an  appar- 
ently good  state  of  preservation,  it  seems  to  follow  that  these  areas  when 
large  must  nevertheless  have  fairly  good  communications  with  the  vas- 
cular system.  That  they  are  probably  not  in  free  communication  with  the 
arteries,  however,  seems  to  be  suggested  by  the  fact  that  no  such  com- 
munications could  be  demonstrated  microscopically,  and  that  they  were  not 
injected  from  the  aorta;  unless  the  supposition  that  the  blood  contained 
in  them  prevented  the  entrance  of  the  injection  mass,  can  be  accepted 
as  an  adequate  explanation.  The  adequacy  of  the  latter  explanation  seems 
doubtful,  however,  since,  as  already  stated,  it  is  usually  impossible  to 
demonstrate  arterioles  or  capillaries  opening  directly  into  the  blood  spaces, 
although  the  direct  communication  of  the  latter  with  veins  is  occasionally 
seen.  For  even  in  the  case  of  the  small  and  definitely  circumscribed  blood 
islands,  which  are  completely  surrounded  by  lymphatic  tissue  and  which 
lie  more  or  less  distant  from  neighboring  blood  spaces,  a  direct  communi- 
cation with  the  arterial  system  could  not  be  demonstrated.  Consequently 
it  is  difficult  to  believe  that  such  a  direct  communication,  if  it  occurs  at 
all,  represents  normal  or  at  least  common  conditions. 

THE  CELLULAR  CONTENT 

For  the  purpose  of  studying  the  cellular  content  of  hemal  nodes, 
blood  smears  and  cover-slip  preparations  from  fresh  nodes  and  from  the 
blood  of  the  vein  draining  the  node  were  also  examined.  In  order  to  be 
certain  that  the  veins  from  which  the  blood  was  taken  actually  drained  a 
hemal  node,  injections  into  the  node  were  made  later.  Although  no  full 
discussion  is  here  intended,  the  large  number  of  nodes  examined  and  the 
many  different  staining  methods  used,  afforded  every  opportunity  for  a 
comprehensive  study  of  the  cellular  content. 

As  is  well  known,  the  ordinary  lymphocytes  form  the  great  bulk  of 
the  parenchyma  of  most  nodes.  Small  areas  in  which  they  mingled  in 
anything  like  equal  proportions  with  erythrocytes  were  only  rarely  found. 


CELLULAR   CONTENT  43 

and  specimens  in  which  such  intermingling  occurred  throughout  an  entire 
node,  or  an  entire  section  even,  were  still  less  frequent.  Although  a  good 
deal  of  intermingling  occurred  in  some  specimens,  both  lymphocytes  and 
erythrocytes  were  segregated  more  or  less  distinctly  as  a  rule;  and  even 
in  nodes  which  contained  but  remnants  of  lymphatic  tissue  the  lympho- 
cytes were  formed  into  small  circumscribed  areas  or  groups  near  the 
radicles  of  the  venous  system.  The  constancy  in  staining  characters  jf 
the  lymphocytes  was  in  striking  contrast  to  that  of  the  erythrocytes  and 
acidophiles.  However,  in  nodes  which  practically  represented  a  sac  of 
blood  in  which  the  small  remaining  masses  of  lymphocytes  were  sur- 
rounded more  or  less  completely  by  remnants  of  the  framework  of  the 
node,  both  protoplasm  and  nuclei  of  the  lymphocytes  occasionally  assumed 
very  irregular  shapes.  In  other  cases  the  nuclei  stained  poorly,  and  the 
nuclear  network  was  indistinct;  while  in  still  others  they  were  pyknotic 
or  had  apparently  fragmented. 

Variations  in  the  size  of  the  lymphocytes  within  the  same  or  in  differ- 
ent nodes  were  considerable;  but  often  these  were  apparent  and  not  real, 
for  these  fluctuations  were  chiefly  due  to  variations  in  the  size  of  the  nu- 
clei, rather  than  to  differences  in  the  quantity  of  cytoplasm  present.  Since 
however,  the  cell  outlines  were  very  frequently  indistinct,  while  those  of 
the  nuclei  were  well  defined,  these  observations  were  not  wholly  satisfac- 
tory. The  protoplasm  was  often  not  eccentric;  and  where,  as  in  case 
of  the  center  of  the  follicles,  the  cells  were  closely  packed,  they  were  much 
larger,  had  vesicular  nuclei,  and  frequently  a  more  or  less  polygonal 
outline.  The  size  and  number  of  the  chromatin  granules  varied  greatly, 
the  smaller  ones  being  more  common  near  the  periphery  of  the  nucleus, 
while  the  larger  ones,  on  the  contrary,  lay  nearer  the  center.  The  chro- 
matin network  too  was  often  quite  distinct,  but  well-defined  nucleoli  were 
infrequent.  Moreover,  the  nuclei  of  cells  which  lay  near  the  periphery 
of  the  follicle,  were  usually  more  regular  in  shape,  and  were  often  entirely 
filled  with  granules ;  while  those  nearer  the  center,  besides  usually  being 
vesicular,  larger,  and  more  irregular  in  shape,  contained  but  few  granules. 
Unmistakable  mitotic  figures  could  not  always  be  found  in  the  follicles, 
and  still  less  frequently  in  other  parts  of  the  nodes.  Since,  however,  a 
comparatively  small  number  of  specimens  were  prepared  for  this  partic- 
ular purpose,  these  statements  may  not  be  thoroughly  representative. 

The  apparently  excellent  state  of  preservation  of  the  blood,  in  both 
the  parenchyma  and  subcapsular  blood  spaces,  in  the  great  majority  of 
nodes,  is  in  marked  contrast  to  the  degenerated  condition  frequently 
observed  in  the  lacunae  of  Weidenreich  or  true  venous  sinuses.  Nucleated 


44  HEMOLYMPH    NODES    OF    THE    SHEEP 

red  cells  were  found  nowhere,  however,  save  in  foetal  nodes.  Although 
the  erythrocytes  were  generally  well  preserved,  all  gradations  between  per- 
fect cells  and  small  masses  of  cell  detritus  were  found  in  specimens  pre- 
pared in  many  different  ways.  As  might  be  expected,  however,  they  were 
frequently  well  preserved  in  nodes  depleted  of  lymphatic  tissue ;  although 
the  absence  of  fragments  of  erythrocytes  within  these  nodes  may  have 
been  due,  in  part  at  least,  to  the  freer  circulation  which  must  exist  in 
them  and  which  assures  a  freer  drainage  of  the  node.  In  some  specimens 
which  were  only  partially  filled  with  lymphocytes  and  blood,  many  eryth- 
rocytes assumed  most  unusual  shapes,  which  probably  cannot  be  attrib- 
uted to  poikilocytosis.  In  some  Zenker  preparations,  for  example,  many 
isolated  cells  which  were  not  crowded  upon  by  others  were  truly  cup- 
shaped,  as  has  been  variously  observed.  The  outlines  of  others  were 
ovoid,  or  crescentic ;  while  still  others  looked  as  though  the  cell  mem- 
brane had  ruptured,  and  retracted  somewhat,  thus  leaving  an  open- 
ing with  an  irregularly  torn  margin.  Among  these  cup-shaped  cells  some 
fragments  of  erythrocytes  were  always  found ;  but  most  of  them  stained 
no  differently  than  the  normally-shaped  ones.  Aside  from  this  disinte- 
gration, the  erythrocytes,  particularly  in  nodes  depleted  of  much  of  the 
lymphatic  tissue,  also  exhibited  some  variability,  in  staining  characters. 
In  Zenker  preparations,  most  of  them  usually  stained  a  golden  yellow  with 
orange  G ;  but  groups  or  areas  of  others  took  the  pink  of  Congo  red  or 
eosin;  and  practically  all  gradations  in  staining  reactions  were  found  be- 
tween these  colors.  The  best-preserved  cells  usually  stained  with  orange 
G,  as  was  the  case  in  embryonic  nodes ;  although  it  must  be  added  that 
irregularly  shaped  erythroblasts  contained  in  the  latter,  occasionally 
stained  pink.  Since,  however,  unmistakable  fragments  of  erythrocytes 
also  often  stained  pink,  it  may  be  inferred  that  this  selective  staining 
quality  on  part  of  some  erythrocytes  probably  signifies  little  else  than  in- 
cipient degeneration.  Since  some  of  the  fragments  of  erythrocytes  were 
circular  in  outline,  they  simulated  blood  platelets  so  closely  that  if  found 
in  circulating  blood  they  would  in  ordinary  preparations  probably  be  in- 
distinguishable from  them.  Although  it  was  sometimes  difficult  or  im- 
possible to  stain  the  erythrocytes  in  the  blood  spaces  satisfactorily,  it  is 
doubtful  whether  this  fact  can  be  attributed  to  a  deficiency  in  hemaglobin, 
as  held  by  Meek  [17],  in  case  of  cells  from  pathological  glands  taken  from 
the  human  body. 

Polymorphonuclear  leucocytes  were  common,  especially  in  some  parts 
of  the  parenchyma  and  in  the  veins.  They  were  rather  uncommon  in  the 
blood  islands  and  in  the  peripheral  blood  space,  and  were  not  observed 


CELLULAR   CONTENT  45 

in  the  follicles,  save  when  these  contained  blood.  Large  mono-nuclear 
leucocytes  were  found  frequently  in  the  lymphatic  tissue,  and  in  greater 
numbers  in  cover-slip  preparations  taken  from  the  vein  draining  a  node. 
In  the  arteries,  on  the  other  hand,  and  in  the  blood  islands,  they  were 
found  in  smaller  numbers  only. 

Although  individual  phagocytes  could  usually  be  found,  marked 
phagocytosis  was  not  a  constant  phenomenon.  In  some  cases,  however, 
the  whole  section  was  dotted  with  scattered  polymorphonuclear  leuco- 
cytes, which  were  filled  with  fragments  of  erythrocytes  and  fairly 
well  preserved  cells.  These  phagocytic  leucocytes  were  not  much  en- 
larged, as  a  rule,  and  were  always  well  preserved.  In  some  cases,  how- 
ever, so  many  and  such  extremely  large  phagocytes  were  present  that  the 
whole  section  of  a  node  was  seen  to  be  studded  with  them  on  lower  power 
(x  42)  magnification.  Since  these  large  cells  were  filled  so  completely 
with  erythrocytes  and  fragments  of  such,  they  gave  the  section  the  ap- 
pearance of  containing  numerous  small  blood  islands  or  areas.  The  nu- 
clei of  these  large  endotheloid  cells,  a  group  of  which  was  sometimes 
contained  in  a  follicle,  were  large,  oval  and  vesicular.  Occasionally  simi- 
lar isolated  cells  were  found  in  small  numbers,  in  the  hemal  areas  of  nodes 
in  which  phagocytosis  by  polymorphonuclear  leucocytes  was  very  active; 
but  this  association  was  not  at  all  constant. 

Besides  typical  eosinophiles,  which  were  sometimes  exceedingly  nu- 
merous and  rarely  arranged  around  an  artery  (see  fig.  26),  others  with 
less  evident  granules  were  not  uncommonly  present.  These  were  usually 
most  evident  in  sections  of  nodes  fixed  in  acetic  bichloride  and  stained  in 
haemotoxylin  followed  by  rubin  S.  Besides  these  atypical  eosinophiles, 
other  generally  much  larger  acidophile  cells  with  vesicular  and  occasion- 
ally pyknotic  nuclei,  were  also  found  in  developing  and  mature  nodes. 
They  varied  considerably  in  size,  and  were  undoubtedly  phagocytic  in 
some  cases. 

The  most  uncommon  cells  found  in  the  course  of  this  investigation 
were  of  course  the  poly-  and  megakaryocytes,  of  varying  sizes  and 
shapes.  Some  of  these  multi-nucleated  ( ?)  cells  were  extremely 
large,  and  had  a  very  irregular  outline.  In  fact  they  were  rarely  so  irreg- 
ular that  the  outlying  portions  suggested  the  occurrence  of  pseudopods 
and  amoeboid  motion.  These  cells,  which  were  usually  found  in  the 
lymphatic  tissue,  were  sometimes  surrounded  more  or  less  completely  by 
an  empty  space  of  varying  width,  which  was,  however,  seldom  so  large 
as  to  accommodate  additional  cells.  Although  more  numerous  in  devel- 
oping nodes,  there  was  nothing  which  indicated  that  they  are  character- 


46  HEMOLYMPH    NODES    OF    THE    SHEEP 

istic  of  any  particular  type  of  node,  or  that  they  are  confined  to  any  par- 
ticular stage  of  development.  They  were  present  in  foetal  nodes,  in  those 
from  young  lambs,  and  in  those  from  adult  sheep  as  well.  Usually  they 
lay  somewhat  isolated,  though  rarely  a  group  of  three  or  four  was  found. 
They  varied  much  in  size,  a  single  section  of  the  largest  extending  half- 
way across  the  field  of  a  No.  5  ocular  and  homogeneous  immersion  (Zeis) 
and  through  a  thickness  of  10-500.;  the  largest  measuring  30x50x30^  by 
filar  micrometer.  The  protoplasm,  which  was  non-granular,  took  an  eosi- 
nophile  stain  and  was  not  surrounded  by  a  recognizable  cell  membrane. 
Rarely  a  somewhat  hyaline  border,  suggesting  degenerative  changes,  was 
noticeable.  The  vesicular  well  defined,  apparently  separate,  nuclei,  were 
generally  circular  or  irregularly  oval  in  shape,  had  a  distinct  nuclear  mem- 
brane, and  varied  from  about  5  to  20  u  in  size.  When  large  and  single, 
the  nucleus  was  frequently  lobed  or  crenated ;  and  when  multiple,  as  many 
as  six  could  often  be  seen  without  a  change  of  focus,  assembled  in  the 
center  or  scattered  about  at  random  in  the  protoplasm.  The  chromatin 
granules  in  the  nucleus  were  few  and  small,  the  nuclear  network  indis- 
tinct, and  mitotic  figures  or  conclusive  evidences  of  amitosis  were 
never  observed.  However,  since  only  a  comparatively  small  number  of 
these  giant  cells  could  be  observed,  it  would  be  unjust  to  over-emphasize 
these  facts.  Vacuoles  were  seen  only  occasionally ;  but  some  cells  seemed 
crowded  with  inclusions,  some  of  which  simulated  erythrocytes  and  plate- 
lets quite  closely ;  while  still  other  areas  looked  like  local  condensations  in 
the  protoplasm,  which  in  the  stains  used  suggested  areas  of  degeneration, 
some  of  which  looked  not  unlike  Negri  bodies.  In  some  cases  these  local 
condensations  or  degenerations  which  stain  a  deeper  pink  are  surrounded 
by  a  clear  area  or  halo,  which  gives  the  whole  structure  a  superficial 
resemblance  to  a  nucleated  cell ;  and  in  other  cases  such  were  actually 
included  in  the  periphery  of  the  protoplasm. 

Plasma  cells  were  found  in  small  numbers  in  some  of  the  specimens 
only.  They  were  demonstrated  most  successfully  by  Unna's  polychrome 
methylene  blue,  after  fixation  and  hardening  in  alcohol.  Preparations 
were  also  stained  according  to  Ehrlich,  Ehrlich  and  Westphal,  and  also 
by  Unna's  polychrome  methylene  blue  followed  by  orcein ;  but  the  results 
obtained  by  these  stains  were  not  as  satisfactory.  There  was  nothing  char- 
acteristic about  their  distribution  or  structure,  for  isolated  specimens  were 
scattered  about  at  random,  and  were  also  found  in  some  of  the  follicles. 
I  do  not  regard  their  presence  as  unusual  or  specially  significant,  or  in- 
dicative of  inflammatory  changes,  for  the  nodes  were  normal  specimens. 

Mast  and  iron  containing  cells  were  never  found,  although  special 


MIXED   NODES  47 

methods  were  used  and  repeated  examinations  made;  and  pigmented 
cells  were  seen  but  seldom.  In  the  search  for  iron,  for  example,  all 
known  methods  were  used,  without  a  single  positive  result  being  obtained. 
However,  since  Weidenreich  [38]  found  lumps  of  pigment  of  a  brownish- 
yellow  color  which  gave  the  reactions  in  sections  treated  for  inorganic 
iron  with  ferrocyanide  and  hydrochloric  acid  and  also  with  ammonium 
sulphohydrate,  it  is  possibe  that  there  is  considerable  variation  with  re- 
spect to  the  presence  of  iron,  or  that  the  nodes  under  observaion  were  not 
hemal  nodes.  This  supposition  also  receives  some  support  from  the  ob- 
servation of  Weidenreich  that  only  a  particular  type  of  cell,  designated 
as  a  "direct  hemophage"  by  him,  contained  inorganic  iron.  I  am  con- 
vinced, however,  that  not  every  cell  which  might  justly  be  regarded  as  a 
direct  hemophage  gives  the  ferro-cyanide-iron  reaction.  In  fact  none  of 
these  cells,  in  the  large  series  of  nodes  examined,  gave  this  reaction.  In 
the  search  for  other  pigment  no  special  methods  were  used,  since  ample 
opportunity  for  its  detection  was  afforded  by  the  many  different  methods 
of  fixation  and  staining  used.  The  great  majority  of  hemal  nodes  con- 
tained no  pigment ;  but  a  group  of  peculiar  and  uncommon  lymph  nodes, 
which  will  be  discussed  presently  under  the  designation  of  mixed  nodes, 
contained  very  much  pigment.  However,  only  about  a  dozen  of  these 
nodes  were  found,  among  many  hundred  specimens  examined.  Indeed, 
the  absence  of  pigment  is  an  important  characteristic  of  typical  hemal 
nodes,  and  is  particularly  interesting  because  such  decided  destruction  of 
erythrocytes  apparently  occurs  in  so  many  of  them,  v  Schumacher 
too  called  attention  to  the  fact  that  pigment  is  usually  absent  in  the  hemal 
nodes  of  the  sheep. 

THE  QUESTION  OF  MIXED  NODES 

As  already  stated  and  emphasized,  the  exceedingly  protean  character 
of  hemal  nodes  often  makes  it  difficult  or  impossible  even  to  distinguish 
them  from  lymph  nodes  by  inspection,  or  even  by  microscopical  examina- 
tion of  a  few  sections.  Because  of  this  difficulty,  no  doubt,  the  supposition 
that  mixed  or  true  hemolymph  nodes  exist  seemed  justifiable  to  many 
investigators.  Helly  [n],  Forgeot  [6  and  7],  and  v  Schumacher 
[27],  for  example,  stated  that  all  transitions  can  be  found  in  the  sheep, 
from  glands  with  lymphatics  to  those  without  them.  Warthin  [34]  and 
35]  made  a  similar  statement  regarding  lymph  nodes  in  general;  and 
Forgeot  even  insisted  that  injections  are  unnecessary  to  demonstrate  the 
presence  of  lymphatics  in  hemolymph  nodes.  Forgeot  nevertheless 
stated  that  hemolymph  glands  may  be  wholly  without  lymphatic  connec- 
tions, and  also  that  the  lymphatics  join  the  developing  hemolymph  node 


48  HEMOLYMPH    NODES    OF    THE    SHEEP 

later;  while  v  Schumacher  concluded  that  they  lose  them.  Similarly 
for  man  Warthin  [33]  stated  that  he  found  combination  forms  of 
spleeno-  and  marrow  lymph  nodes,  as  well  as  all  manner  of  transitions 
between  spleno-lymph  glands  and  lymph  glands  and  the  spleen.  Warthin 
[33] — and  later  Lewis  [13  and  14] — further  stated  that  there  may  be 
blood  sinuses  in  one  part  of  a  node  and  lymph  sinuses  in  the  other ;  and 
Warthin  [31]  added  that  "transitional  forms  cannot  be  distinguished 
from  congested  lymph  glands."  If  this  be  true,  then  the  question  as 
to  how  it  is  known  that  true  hemolymph  nodes,  i.  e.,  nodes  other  than 
lymph  nodes,  in  similar  relation  to  both  the  lymphatic  and  the  vascular 
systems  as  that  of  lymph  nodes  to  the  lymphatic  system — i.  e.,  having 
sinuses  common  to  both  systems — occur  at  all,  seems  a  pertinent  one. 
For  if  transitional  forms  cannot  be  distinguished,  what  basis  is  there 
for  any,  not  to  say  an  elaborate,  classification?  Meek,  who  studied  the 
lymph  and  hemolymph  glands  of  man  in  pathological  states,  declares 
somewhat  similarly,  that  "In  a  few  cases  where  hemolymph  glands  were 
present  (Meek  does  not  state  how  they  were  identified  as  such)  in  large 
numbers,  I  have  removed  and  examined  all  the  easily  found  lymphatic 
glands  of  the  same  group,  and  found  them  all  to  show  a  practically 
identical  condition." 

It  is  not  clear,  to  be  sure,  how  identification  of  and  differentiation 
between  lymph  and  hemolymph  nodes  in  "identical  condition"  was  possi- 
ble. Nevertheless,  Meek  continues :  "It  appears,  then,  that  every 
lymphatic  gland  is  a  potential  haemolymph  gland.  The  experimental 
production  of  such  glands  in  the  guinea-pig  is  easy  of  accomplishment. 
.  .  ."  According  to  Meek,  then,  a  hemolymph  node  is  only  a  lymph 
node  under  abnormal  or  altered  conditions.  That  is,  any  lymph  node 
subjected  to  an  injury  or  to  abnormal  conditions  either  in  disease  or 
experimentally,  can  quickly  be  converted  into  a  hemolymph  node!  This 
would  also  seem  to  be  Retterer's  conclusion  regarding  the  nodes  of 
guinea-pigs,  which  conclusions  are  discussed  elsewhere*  with  Meeks' 
results,  in  connection  with  the  writer's  findings  and  experiments  on  these 
animals  and  on  dogs.  Meek,  although  speaking  of  two  kinds  of  nodes 
and  of  the  conversion  of  one  into  the  other,  concluded,  however,  in 
direct  contradiction  to  Warthin  and  to  himself,  that  there  is  no  justi- 
fication for  classifying  human  nodes  as  lymphatic  and  hemolymphatic. 
A  similar  conclusion  regarding  the  relation  between  lymph  nodes  and 
hemal  nodes  was  reached  by  Retterer  [22],  who  stated,  in  short,  that 
all  lymphatic  nodes  possess  the  same  structure  and  functions,  and 

*  Journal  of  Experimental  Zoology,  1914,  and  Anatomical  Record,  1914. 


MIXED  NODES  49 

whether  they  contain  blood  or  not  depends  only  upon  the  force  of  the 
lymph  stream.  It  suffices  to  change  the  arterial  pressure,  and  conse- 
quently the  lymph  pressure,  in  order  to  convert  a  gland  from  lymph  to 
haemolymph  gland,  and  vice  versa.t 

(  In  the  course  of  this  investigation  only  a  few  observations  were  made 
on  human  nodes ;  but  as  far  as  these  and  the  examination  of  nodes  from 
bovines,  goats,  dogs,  cats,  rabbits  and  guinea-pigs  were  concerned,  no 
evidences  whatever  for  the  existence  of  combination  forms  or  the  con- 
version of  one  into  the  other,  have  been  obtained.  Because  of  the 
comparatively  small  size  of  the  hemal  nodes  in  most  of  the  domestic 
animals  injections  were  made  only  on  the  sheep,  bovines  and  in  a  few 
goats.* 

Some  of  the  lymph  nodes  which  are  indistinguishable  often  from 
hemal  nodes  save  by  injection  methods,  are  comparatively  large  speci- 
mens which  have  the  color  of  certain  hemal  nodes  at  one  end  and  of 
lymph  nodes  at  the  other.  Although  these  hemorrhagic  or  hemal  por- 
tions are  often  irregular  in  outline  and  occasionally  ill  defined  in  many 
cases,  they  are  nevertheless  quite  well  defined  to  the  unaided  eye.  In 
some  cases  this  hemorrhagic  area  is  confined  to  the  interior  of  the  larger 
nodes,  and  is  consequently  not  evident  on  external  examination  alone. 
In  addition  to  such  specimens,  others  which  represent  all  shades  in  color 
from  the  gray  of  lymphatic  nodes  to  a  chocolate-brown  or  a  magenta-red, 
are  not  very  uncommon.  Still  others  are  so  deeply  pigmented  that  they 
are  black,  and  at  once  suggest  anthracosis.  These  dark  pigmented  nodes 
also  may  simulate  rare  hemal  nodes  in  external  appearance,  and  hence 
may  likewise  suggest  the  occurrence  of  an  intermediate  group  of  mixed 
nodes. 

Lewis  [13]  also  emphasized  the  fact  that  intermediate  forms  are 
very  numerous,  and  strangely  enough  referred  to  glands  in  ungulates 
"Many  of  the  largest  of  which  are  (9-10  cm.)  long  and  have  a  cer- 
tain structure  recently  described  by  Weidenreich."  The  latter  is  then 
said  to  have  described  an  intermediate  form,  having  blood  sinuses  only  in 
one  portion  of  the  node  and  lymph  sinuses  only  in  the  rest,  each  kind 
of  sinus  occupying  a  distinct  portion  of  the  node.  Although  emphasiz- 
ing the  fact  that  there  are  ordinary  lymph  glands  in  which  ".  .  .  very 
similar  and  easily  mistaken  appearances  are  presented,"  Lewis  further 

tSee  also  Retterer,  Edouard:  Des  hematics  des  mammiferes.  Jr.  de  I'anat. 
et  de  physiol.  Tome  XLIII,  1907. 

tHemal  nodes  were  not  found  in  cats,  dogs,  rats,  rabbits  and  guinea-pigs 
unless  we  regard  them  as  identical  with  supernumerary  spleens. 


50  HEMOLYMPH    NODES    OF    THE    SHEEP 

states  that  there  rarely  are  other  transition  forms,  in  which  there  is  a 
mixture  of  blood  and  lymph  streams  in  one  portion  and  only  lymph  in 
the  sinuses  of  the  rest  of  the  node,  on  the  other  hand ;  and  cases  in  which 
both  streams  mingle  in  one  portion,  while  the  rest  of  the  node  contains 
blood  sinuses  only. 

Vincent  also  believed  in  the  existence  of  nodes  having  sinuses  com- 
mon to  the  lymphatic  and  vascular  systems,  as  also  Robertson  had  pre- 
viously stated. 

Some  of  the  difficulties  in  identification  met  with  in  gross  appear- 
ance are  likewise  encountered  upon  microscopical  examination  of  sepa- 
rate sections ;  but  if  a  group  of  mixed  or  transitional  nodes  really  existed 
with  sinuses  common  to  the  vascular  and  lymphatic  circulations,  it  is 
clear  that  it  should  be  possible  to  inject  both  the  lymphatics  and  the 
veins  from  them.  For,  as  is  well  known,  puncture  of  a  lymph  node 
always  results  in  the  injection  of  the  lymphatic  and  not  the  vascular 
circulation  of  the  node — except  accidentally,  and  only  very  rarely; 
while,  as  has  been  amply  established,  puncture  of  hemal  nodes,  on  the 
contrary,  always  results  in  injection  of  the  veins  draining  the  node,  and 
occasionally  the  vein  draining  an  adjacent  node,  but  never  the  lymphatics. 
Hence,  if  mixed  or  true  hemolymph  nodes  existed,  the  injection  mass 
should  appear  both  in  the  vena  cava  and  in  the  thoracic  duct.  Such 
was,  however,  never  the  case;  and  after  a  little  experience  it  was  quite 
possible  indeed  to  foresee,  in  most  cases  at  least,  what  the  results  of  punc- 
ture injections  into  a  given  questionable  node  in  situ  on  the  fresh  carcass 
would  be.  For  example,  the  microscopically  pigmented  nodes  which 
suggest  anthracosis,  were  generally  found  in  connection  with  the  lym- 
phatic system.  The  same  was  also  true  of  rare  and  rather  large  nodes 
found  in  the  sub-lumbar  region  in  sheep,  a  portion  of  which  was  typic- 
ally lymphatic  in  color  and  the  rest  quite  as  typically  hemal.  If  these 
large,  apparently  combination  forms,  were  true  hemolymph  nodes,  it 
should,  of  course,  have  been  possible  to  inject  at  least  the  lymphatic  ves- 
sels from  the  typically  appearing  lymphatic  portion,  and  the  veins  from 
the  typical  hemal  portion.  However,  this  was  never  possible.  Such 
nodes  in  the  sheep  were  found  to  be  either  in  connection  with  the  vascu- 
lar or  with  the  lymphatic  system,  but  never  with  both,  and  usually  with 
the  latter;  nor  has  anyone  injected  the  veins  from  one  and  the  lymphatics 
from  the  other  portion. 

Since  the  only  reliable  criterion — the  injection  method — for  distin- 
guishing a  lymph  from  a  hemal  node,  was  accepted  only  as  a  result  of 
experiments,  and  is  not  a  theoretical  or  preconceived  one,  it  follows,  to 


MIXED  NODES  51 

be  sure,  that  the  above  results  demonstrate  that  the  mere  presence  or 
absence  of  free  blood  in  the  form  of  blood  islands  or  intermingled  with 
the  parenchyma  cannot  and  does  not  convert  a  lymph  node  into  a  hemal 
node.  For  if  this  were  the  case  then  there  could,  of  course,  be  no  such 
organs  as  true  hemal  nodes.  The  fundamental  difference  between  lymph 
and  hemal  nodes,  as  pointed  out  and  reiterated  by  Weidenreich,  is  the 
presence  or  the  absence  of  lymphatics.  It  does  not  consist  of  or  lie  in  a 
mingling  of  the  vascular  and  lymphatic  circulations  of  the  node,  or  in 
the  possession  of  sinuses  and  blood  spaces  common  to  both;  nor  merely 
in  the  presence  of  blood  in  the  lymph  spaces  of  lymph  nodes.  Further- 
more, there  is  another  fundamental  difference  between  hemal  and  lymph 
nodes  which  has  been  overlooked  so  far,  but  to  which  attention  was  di- 
rected earlier  in  this  discussion.  It  was  emphasized  in  connection  with 
injections  that,  as  is  well  known,  in  mature  lymph  nodes  injected  from 
the  vascular  system,  the  transition  from  the  artery  to  the  vein  is  a  very 
gradual  one.  These  injections  of  the  vascular  system  present  many  fine 
arborizations,  as  is  characteristic  of  the  vascular  system  in  general.  In 
the  case  of  hemal  nodes,  on  the  contrary,  there  apparently  is  no  such 
gradual  transition  by  means  of  capillaries,  but  by  very  wide  sinuses, 
devoid  of  reticulum  and  having  walls  like  capillaries.  These  open  di- 
rectly into  the  draining  vein,  and  communicate  with  the  parenchyma  and 
indirectly  with  the  blood  spaces.  Hence  it  is  evident  that  in  order  to 
change  a  lymph  into  a  hemal  node  it  is  not  only  necessary  to  remove  the 
characteristic  lymph  sinuses  and  lymph  vessels,  but  to  profoundly  alter 
the  vascular  system.  This  fact  and  the  fact  that  the  distribution  of  the 
blood  spaces — the  so-called  peripheral  and  central  sinuses  of  hemal  nodes 
— which  are  considered  comparable  to  the  lymph  sinuses  in  lymph 
nodes,  have  a  wholly  different  distribution,  and  do  not  as  a  rule  form 
a  communicating  system,  is  also  overlooked  by  v  Schumacher,  who  con- 
cluded that  an  alteration  in  or  an  obliteration  of  the  lymphatics  is  all 
that  is  required  to  convert  a  lymph  node  into  a  hemal  node. 

Hemal  nodes  in  which  the  lymphatics  ended  blindly  in  the  hilus,  as 
reported  by  Helly,  or  in  the  capsule,  as  reported  by  v  Schumacher  and 
denied  by  Helly,  or  in  which  all  stages  of  partial  penetration  of  the  nodes 
by  lymph  vessels  occurred,  were  not  found.  Lymphatics  were  either 
present  or  wholly  absent  in  all  nodes  examined  experimentally  or  micros- 
copically; and  whatever  explanation  or  explanations  it  may  be  possible 
to  give  for  the  occurrence  of  so-called  hemorrhagic  lymph  nodes, — the 
occurrence  of  which  no  one  doubts — i.  e.,  nodes  in  which  blood  cells 
are  present  in  the  lymphatic  sinuses  and  parenchyma — it  must  be  evi- 


52  HEMOLYMPH    NODES    OF    THE    SHEEP 

dent,  of  course,  that  congestion  or  hemorrhage  or  diapedesis  in  an  organ 
does  not  change  the  essential  morphological  identity  of  that  organ. 

Upon  microscopical  examination  most  of  these  apparently  transi- 
tional forms  were  found  to  contain  no  lacunae  of  Weidenreich  (true 
venous  sinuses)  or  large  blood  islands  or  blood  spaces.  In  addition  to 
portions  of  the  parenchyma  which  looked  like  splenic  tissue  devoid  of 
Malpighian  corpuscles,  or  which,  on  the  contrary,  consisted  of  an  almost 
solid  mass  of  lymphatic  tissue,  they  contained  areas  in  which  a  great 
deal  of  golden  pigment,  and  more  rarely  many  oxyphile  cells,  were  pres- 
ent. The  partly  depleted  nature  of  certain  of  these  nodes,  and  especially 
the  presence  in  them  of  much  brassy  pigment  and  the  occurrence  of 
abundant  phagocytosis,  gave  a  very  peculiar  appearance  to  a  section. 
Because  of  the  open  character  of  the  parenchyma,  they  simulated  lymph 
nodes  much  more  closely  microscopically  than  hemal  nodes.  Since 
phagocytosis  is  a  very  noticeable  feature  in  these  specimens,  it  does  not 
seem  impossible,  to  me,  that  Lewis's  [14]  observations  regarding  the 
relative  frequency  of  phagocytosis  in  the  spleen  to  that  in  the  hemal 
nodes,  was  based  on  observations  on  this  type  of  lymph  node.  This 
supposition  gains  in  probability  by  the  observations  made  on  patho- 
logical human  lymph  nodes  by  Warthin  and  Meek,  to  the  effect  that 
the  degree  of  pigmentation  varies  with  the  amount  of  hemolysis ;  and  also 
by  the  observations  of  v  Schumacher  regarding  the  comparative  infre- 
quency  of  phagocytosis  in  hemal  nodes.  Meek  also  speaks  of  the  occur- 
rence of  "yellow  or  light  brown  pigment,  usually  confined  to  the  sinuses 
though  rarely  found  in  the  germ  centers."  Meek  also  found  that  even 
in  these  pathological  human  nodes  the  reactions  for  free  iron  were  very 
variable,  and  in  the  majority  of  cases  not  obtained,  though  occasionally 
the  presence  of  a  large  amount  of  free  iron  could  be  established.  These 
findings  of  Meek  are  in  entire  accord  with  what  was  found  by  the  writer 
in  intensely  congested,  apparently  hemal  nodes,  found  along  the  common 
iliac  vessels  in  the  carcass  of  a  sheep  which  had  been  seriously  torn  in 
the  gluteal  region  by  dogs,  and  in  another  which  died  of  septicaemia. 
The  first  sheep  was  bled  to  death  after  necrosis  had  set  in  at  the  site  of 
injury,  some  days  after  having  been  attacked.  At  necropsy  it  was  found 
that  practically  all  the  pelvic  and  prevertebral  lymph  nodes  were  hemal 
in  color,  and  could  probably  not  have  been  identified  positively  by  micros- 
copic examination  alone;  yet  by  injections  it  was  easily  shown  that  they 
were  lymph  nodes  in  direct  connection  with  the  lumbar  lymphatics  and 
the  thoracic  duct.  The  dilated  lymphatics  going  to  these  nodes  were 
plainly  visible,  and  were  tinged  with  blood.  It  would  be  ridiculous,  to 
be  sure,  to  assume  that  simply  because  this  animal  had  been  attacked  by 


MIXED   NODES  55 

a  dog  or  dogs — and  what  matters  it  whether  the  attacking  agent  is  a 
dog,  a  disease,  or  an  experimenter? — these  lymph  nodes  had  been  con- 
verted into  hemal  nodes.  In  a  second  sheep  similar  conditions  were 
found,  and  similar  results  obtained. 

In  addition  to  small  quantities  of  lymphatic  tissue  intermixed  with 
blood  and  pigment,  some  of  the  apparently  mixed  nodes  found  in  sheep 
contain  extremely  large  connective  tissue  septa  and  trabeculae,  and  the 
walls  of  some  of  the  arteries  are  many  times  the  ordinary  thickness. 
These  connective  tissue  septa  are  rarely  so  thick  and  so  extensive  that 
they  could  be  seen  with  the  unaided  eye,  to  divide  a  section  of  a  node 
4-6  mm.  in  size  into  more  or  less  distinct  portions.  Sometimes,  also, 
large  masses  of  connective  tissue  lay  here  and  there  under  the  cap- 
sule, although  not  continuous  with  it.  In  other  Instances,  although 
not  evident  to  the  unaided  eye,  the  total  amount  as  well  as  the  relative 
proportions  of  the  connective  tissue  were  smaller  than  usual,  and  located 
mainly  in  the  center  of  the  node.  Frequently,  also  small  numbers  of 
erythrocytes  and  lymphocytes  were  scattered  about  miscellaneously  in 
the  connective  tissue  septa. 

The  arteries  with  greatly  thickened  walls  were  found  almost  exclu- 
sively in  areas  very  largely  devoid  of  lymphocytes  and  erythrocytes.  No 
sclerotic  or  atheromatous  changes  were  seen.  The  intima  was  normal  or 
practically  so,  and  the  thickening  of  the  wall  was  due  entirely  to  an  in- 
crease in  thickness  of  the  muscular,  and  chiefly  of  the  adventitial  coats. 
Although  slight  variations  in  staining  power  were  observed,  this  thicken- 
ing of  the  wall  was  probably  of  no  significance  with  respect  to  the  char- 
acter of  the  node,  even  if  it  was  correlated  with  its  functional  activity. 

Many  of  the  erythrocytes  scattered  about  in  these  depleted  areas 
showed  degenerative  changes ;  but  in  those  portions  of  the  sections  of 
the  node  which  had  more  the  appearance  of  hemal  nodes  and  where  they 
were  more  numerous,  they  were  better  preserved.  These  degenerating 
erythrocytes  often  lay  in  groups,  which  sometimes  formed  a  more  or  less 
compact  mass  around  leucocytes.  Only  small,  compact  masses  of  lymph- 
ocytes were  contained  in  the  depleted  portions,  but  their  number  increased 
toward  the  denser  portions  of  the  node,  until  the  inter-follicular  areas 
looked  not  unlike  splenic  tissue  because  of  the  intermixture  of  blood  and 
lymphocytes.  .Between  these  denser  portions  of  parenchyma  small  num- 
bers of  lymphocytes  were  also  scattered  about  among  certain  oxyphile 
cells  and  erythrocytes ;  and  while  follicles  were  found  in  the  empty  por- 
tions, they  were  common  and  frequently  large  in  the  non-depleted  por- 
tions. In  these  areas  the  connective  tissue  septa  were,  as  a  rule,  consider- 


54  HEMOLYMPH    NODES    OF    THE    SHEEP 

ably  thicker  than  usual,  and  a  very  coarse  and  imperfect  reticulum  was 
noticeable  by  means  of  the  ordinary  stains.  It  is,  however,  the  above 
referred  to  acidophile  phagocytic  cells  with  a  hyaline  like  protoplasm 
and  the  presence  of  pigment,  which  gave  sections  of  some  of  these  nodes 
the  prominent  distinguishing  microscopical  characteristics.  These  acido- 
phile cells  are  occasionally  so  numerous  and  so  large  that  they  are  plainly 
evident  under  low-power  magnification.  In  contrast  to  the  lymphocytes 
and  erythrocytes,  they  are  most  abundant  in  the  depleted  portions,  and 
gradually  decrease  in  number  as  the  more  typical  portions  of  the  node  are 
approached.  In  the  depth  of  the  latter  they  are  practically  absent. 
Though  most  of  them  are  fairly  circular  in  outline,  some  are  quite  irregu- 
lar in  form.  In  some  cases  this  irregularity  of  form  seemed  to  be  due 
to  degenerative  changes,  or  slight  lobulation ;  but  many  of  them  had  dis- 
tinct processes,  and  looked  exactly  like  branched  connective  tissue  cells, 
and  must,  I  believe,  be  regarded  as  having  at  least  partly  such  and  a  retic- 
ular  origin.  On  some  of  these  cells  which  lay  isolated,  processes  could 
be  seen  which  were  in  continuity  with  the  coarser  reticulum  or  with  the 
cells  at  the  border  of  the  trabeculae.  In  addition  to  those  shaped  like 
ordinary  branched  connective  tissue  cells,  others  with  a  greatly  elongated 
cell  body  with  a  process  at  each  end  were  also  found.  Although  but  a 
single  terminal  process  or  a  bifurcated  one  was  seen,  as  a  rule,  other  pro- 
cesses may,  of  course,  have  extended  in  other  planes  and  directions.  The 
nuclei  of  these  cells  are  vesicular,  irregularly  oval  in  outline,  fairly  cen- 
tral in  position,  seldom  larger  than  twice  the  size  of  the  erythrocytes,  and 
contain  but  few  chromatin  granules.  Usually  only  one  nucleus  is  present, 
but  it  is  not  uncommon  to  find  polynuclear  cells.  The  cytoplasm,  which 
is  abundant  and  takes  an  acidophile  stain,  is  non-granular  or  nearly  so  in 
non-pigmented  cells ;  but  cell  inclusions  are  very  common.  The  latter 
usually  have  the  form  and  appearance  of  laked  erythrocytes,  and,  if  exter- 
nal appearances  are  a  sufficient  guide,  may  be  designated  positively  as 
such.  One  or  two  such  cellular  inclusions  are  very  common,  and  speci- 
mens with  four  or  more  occasionally  occur.  While  most  of  the  cells  con- 
taining erythrocytes  are  non-pigmented,  many  of  those  without  inclu- 
sions have  a  protoplasm  which  is  very  densely  filled  with  golden  or  brassy 
pigment  granules.  This  intra-cellular  pigment  is  not  confined  to  the  cell 
body,  however,  but  is  also  found  in  some  of  the  processes.  "Although  the 
proportion  of  the  intra-  and  extra-cellular  pigment  varies  considerably  in 
different  nodes,  the  size  of  the  granules  is  quite  uniform.  Special  tests 
for  iron  were  used  repeatedly  on  sections  from  these  pigmented  specimens, 
but  no  positive  results  were  obtained.  It  is  of  particular  interest  in  this 
connection  that  similar  pigment  and  acidophile  cells  undoubtedly  phago- 


GENESIS    OF    INTERMEDIATE    FORMS  55 

cytic  in  function,  are  also  found  in  small  numbers  in  some  typical  lymph 
nodes ;  and  that,  as  far  as  microscopical  appearances  are  concerned,  there 
is  a  striking  similarity  between  the  sections  of  the  latter  and  some  of  the 
specimens  which  simulate  hemal  nodes  so  closely  in  external  and  micro- 
scopical appearances. 

THE  GENESIS  OF  INTERMEDIATE  FORMS 

A  moment's  reflection  will  make  it  evident  that  any  condition  which 
results  in  congestion  or  hemorrhage  or  the  accumulation  of  blood  cells  in 
the  parenchyma  or  the  sinuses  of  lymph  nodes,  will  produce  the  speci- 
mens which  have  been  responsible  for  much  confusion.  In  fact  many 
investigators  frankly  stated  that  they  could  not  distinguish  between  con- 
gested or  hemorrhagic  lymph  nodes  and  hemal  nodes.  Haberer  [10], 
for  example,  stated  that  he  repeatedly  confused  human  lymph  nodes 
which  were  changed  by  sepsis,  with  accessory  spleens  macroscopically 
although  they  were  found  to  be  typical  lymph  nodes  microscopically.  Ha- 
berer also  called  attention  to  the  fact  that  in  emaciated  individuals  nodes 
are  frequenly  found  which  do  not  look  like  spleens  mrcroscopically  be- 
cause they  lack  Malpighian  corpuscles,  but  which  seem  to  be  transition 
forms  resulting  from  pathological  conditions.  Moreover,  it  is  probable 
that  the  changes  observed  in  lymph  nodes  after  splenectomy  by  many,  if 
not  all,  the  early  experimenters,  were  of  septic  origin,  as  Foa  and  Schiff 
held,  and  as  their  own  descriptions  suggest.  Besides,  it  is  apparent  that 
blood  cells  must  be  found  in  the  sinuses  of  lymph  nodes  whenever  the 
afferent  lymphatics  drain  an  area  in  which  such  cells  can  enter  the  lym- 
phatic vessels,  as  in  the  case  of  wounds,  injuries,  inflammations,  etc. 
Retterer  and  Lelievre  [23]  also  showed  that  stasis  of  the  lymph  current 
results  in  the  accumlation  of  blood  cells  in  lymph  nodes.  Hence  these 
authors  conclude  that  hemolymph  nodes  are  only  lymph  nodes  in  which 
there  is  stagnation  of  the  lymph  current.  Retterer  [19],  who  called  at- 
tention to  the  fact  that  "ten  years  since" — thirteen  years — he  reported  the 
constant  presence  of  erythrocytes  in  the  lymph  of  the  dog,  rabbit,  and 
guinea-pig,  says  Forgeot  has  shown  the  same  for  ruminants.  Forgeot  [6| 
also  claimed  to  have  found  nodes  in  the  lumbar  region  of  sheep,  goats,  and 
under  the  pleura  and  pericardium  in  bovines,  from  which  blindly-ending 
efferent  lymphatics  of  various  forms  extended  and  occasionally  returned 
to  the  node.  Retterer  [19]  furthermore  found  that  bleeding*  and  tem- 
porary abstinence  removed  the  blood  cells  from  hemolymph  nodes  and 

*Most  investigators  have  held  the  contrary  for  bleeding. 


56  HEMOLYMPH    NODES    OF    THE    SHEEP 

changed  them  into  ordinary  gray  lymph  nodes;  while  prolonged  absti- 
nence, on  the  contrary,  resulted  in  the  accumulation  of  erythrocytes  in 
lymph  nodes. 

From  these  considerations  it  is  evident  that  many  morbid  and  abnor- 
mal conditions  can  cause  an  accumulation  of  blood  cells  in  the  paren- 
chyma and  sinuses  of  lymph  nodes,  and  that  blood  cells  are  probably  con- 
stantly present  in  the  lymph  of  many,  if  not  of  all  mammals.  From 
observations  made  especially  on  dogs  the  writer  is  also  convinced  that 
there  often  is  a  retrogression,  or  better  a  diffusion,  of  blood  from  the  large 
veins  into  the  large  lymphatic  trunks  at  points  of  juncture,  which  can 
convert  many  of  the  bronchial  and  mediastinal  lymph  nodes  into  so-called 
hemolymph  nodes.t  The  distance  to  which  this  reflow  or  intermixture  of 
venous  blood — or  suspensions  and  solutions  injected  into  the  veins — can 
extend  into  the  lymphatics  is  truly  remarkable,  and  is  discussed  more 
fully  in  an  article  on  the  hemal  nodes  of  dogs,  cats,  etc.  A  similar  retro- 
grade flow  of  chyle  was  noticed  in  several  instances  from  the  large  ab- 
dominal lymphatics  to  the  external  iliac  trunks  almost  up  to  the  inguinal 
ligament  in  dogs.  It  should  also  be  recalled  in  this  connection  that  un- 
usual lymphatico-venous  connections  may  rarely  be  a  factor  in  the  pro- 
duction of  hemorrhagic  lymph  nodes.  It  is  not  my  aim  to  open  an  old 
controversy  regarding  lymphatico-venous  communications,  but  the  evi- 
dences recently  brought  forward  by  Huntington  [no]  in  Macropus  rufus, 
by  McClure  and  Silvester  [16]  for  primates,  carnivora,  rodents,  ungu- 
lates and  marsupials,  by  Silvester  [26]  for  the  monkey,  and  by  Baum  [i] 
for  bovines,  seem  to  confirm,  in  a  measure,  the  early  observations  of 
Wutzer,  Nuhn,  Petrel,  Kaaw,  Kulmus,  Lohmann,  Fauth,  J.  Miiller,  Pan- 
izza,  Meckel  Sr.  and  Jr.,  Steno,  Nuck,  Pequet  and  others  on  man  and  ani- 
mals which  a  partly  justified  skepticism  has  so  far  obstinately  refused  to 
accept.  The  writer  has  not  much  confirmatory  evidence,  but  it  is 
clear  that  where  a  lymph  node  is  intercalated  in  a  lymphatic  circuit, 
in  such  a  way  as  to  have  a  double  communication  with  the  veins,  retro- 
grade diffusion  of  blood  from  the  peripheral  vein  through  a  short  efferent 
lymphatic  into  the  node  can  easily  convert  all  nodes  lying  more  centrally 
on  the  lymphatic  circuit  into  reddened  lymph  nodes,  because  of  an  inter- 
mixture of  blood  and  lymph  in  the  sinuses  of  the  more  centrally  placed 
lymph  nodes.  Such  a  case  was  actually  observed  by  the  writer  in  a  lamb 
in  the  case  of  an  axillary  lymph  node  on  each  side. 

t  Although  Retterer  (Comptes  Rendus  de  I'Assoc.  des  Anat.,  Lyon,  1901)  re- 
jects such  an  explanation  in  referring  to  a  similar  explanation  made  by  Thomas 
Bartholin,  I  am  certain  that  a  reflow  or  diffusion  of  blood  from  the  large  veins 
into  the  lymphatics  occasionally  occurs. 


GENESIS    OF    INTERMEDIATE    FORMS  .          57 

Another  explanation  for  the  occurrence  of  reddened  lymph  nodes 
lies  in  the  old  observation  that  such  a  wide  and  direct  open  communica- 
tion between  the  afferent  and  efferent  lymphatics  of  a  node  may  exist 
directly  through  the  peripheral  sinus,  that  the  active  lymph  current  is 
largely,  even  if  not  wholly,  limited  to  the  latter.  Under  such  circum- 
sances  there  would  be  a  slow  lymph  current  in  the  interior  of  the  node, 
with  consequent  accumulation  of  blood  cells  as  a  result  of  stasis.  That 
nodes  with  such  circulatory  conditions  exist  is  beyond  question,  for  the 
varying  rate  with  which  suspensions  of  India  ink  traverse  a  node  is  quite 
striking.  Were  it  not  for  the  existence  of  such  large  peripheral  sinuses, 
a  great  deal  more  difficulty  would  also  be  experienced  in  injecting  a  series 
of  successive  nodes  from  the  most  peripheral  one,  and  of  accounting  for 
the  ease  with  which  the  thoracic  duct,  even  up  to  its  entrance  into  the 
vein,  can  occasionally  be  injected  from  the  pad  of  the  foot  in  the  cat.  In 
several  instances  this  was  accomplished  with  but  a  small  fraction  of  a 
barrelful  of  India  ink  contained  in  a  hypodermic  syringe  of  2^/2  cc.  vol- 
ume. These  observations  confirm  the  inferences  of  v  Frey  and  Bonders, 
and  also  the  observations  of  Richter  in  the  pig. 

In  looking  about  for  an  explanation  for  the  reddening  of  lymph 
nodes  and  the  presence  of  blood  in  the  sinuses,  Vincent  [29]  said :  "I  have 
not  so  far  studied  the  blood  supply  to  these  glands  by  means  of  injections, 
nor  have  I  succeeded  in  finding  the  blood  vessels  in  direct  communication 
with  the  'lymph'  sinuses  of  the  gland;  but  from  the  large  number  of  red 
corpuscles  sometimes  found  in  them,  I  am  convinced  that  there  must  be 
such  communication."  It  will  be  remembered  that  Meckel  Jr.  and  Sr., 
Lindner,  Fohmann,  Lauth,  and,  of  course,  Lippi,  also  believed  in  the  ex- 
istence of  such  communications,  and  that  Lewis  [13]  claims  to  have 
abundantly  confirmed  such  occurrences  by  observation.  While  making 
thousands  of  injections  of  lymph  nodes,  no  evidence  for  the  existence 
of  such  communications,  whose  accidental  existence  is  therefore  not  de- 
nied, was  obtained  in  the  sheep.  However,  in  young  cats,  in  which  the 
mesenteric  lymph  nodes  are  very  tender,  both  veins  and  lymphatics  were 
not  infrequently  injected  by  puncture  from  a  node.  In  most  instances 
the  lymphatics  were  injected  first,  and  then  the  veins.  Moreover,  in 
guinea-pigs  such  results  are  far  easier  to  obtain,  and  not  infrequently 
the  injection  of  veins  and  lymphatics  is  practically  simultaneous.  Never- 
theless, a  little  experimentation  proves  conclusively  that  these  results  are 
obtained  only  because  the  tender  nodes  are  distended  by  the  injected  mass, 
and  hence  disrupted  by  it,  and  by  the  relatively  large  needle  or  capillary 
tube  used  for  purpose  of  puncture  injections.  Injections  of  these  mesen- 


58         .  HEMOLYMPH    NODES    OF    THE    SHEEP 

teric  nodes  from  the  periphery  never  resulted  in  injection  of  the  veins, 
even  when  the  efferent  lymphatic  trunk  was  clamped. 

From  all  these  considerations  it  is  evident  that  there  is  no  lack  of 
abundant  explanation  for  the  occurrence  of  erythrocytes  in  the  sinuses 
and  parenchyma  of  lymph  node — much  less  for  the  reddening — entirely 
aside  from  questions  of  disease,  the  assumption  of  intra-nodal  lymphatico- 
venous  communications,  or  the  formation  of  erythrocytes  within  lymph 
nodes,  under  normal  conditions. 

CLASSIFICATION 

Saltykow  [25]  and  Retterer,  working  with  human  material,  pro- 
nounced against  the  specific  character  of  the  hemolymph  nodes.  Their 
opinion  was  confirmed  later  by  Vincent  and  JHarrison  [28],  who,  from 
their  work  on  bovines  and  sheep,  concluded  that  hemolymph  glands  are 
modified  lymph  glands,  and  that  they  develop  from  them.  A  similar  posi- 
tion is  taken  by  Meek  [17],  who  declared  that  "it  seems  unreasonable  that 
human  'hemolymph'  glands  should  be  classed  as  a  separate  category."  If 
these  conclusions  are  correct  it  is  evident,  of  course,  that  what  have  been 
repeatedly  described  in  man  as  hemolymph  nodes  are  nothing  but  modified 
lymph  nodes.  However,  Warthin  not  only  distinguished  lymph  and  hemo- 
lymph nodes  in  man,  but  described  three  classes  in  the  latter  and  also 
differentiated  spleno-  and  marrow  lymph  nodes,  both  of  which  classes 
were  said  to  be  in  connection  with  the  lymphatic  system.  In  spite  of 
these  facts,  Warthin  nevertheless  declared  that  only  the  second  class,  or 
marrow  lymph  glands,  were  organs  sui  generis.  Warthin  further  stated 
that  the  long  axis  of  marrow  lymph  nodes  usually  lay  parallel  to  the  adja- 
cent vessel.  How  it  is  possible  to  regard  some  and  not  other  hemal  nodes 
as  organs  sui  generis  while  maintaining  the  occurrence  of  transition  and 
combination  forms,  is  not  clear  to  the  writer.  Nor  is  it  clear  how  those 
who  reported  the  occurrence  of  lymphatics  in  hemal  nodes  satisfied  them- 
selves that  the  assumed  nodes  really  were  hemal  nodes,  or  that  the  lymph 
spaces  really  were  lymphatic  spaces,  without  actually  demonstrating  their 
relation  to  the  lymphatic  system.  In  contrast  to  Warthin,  v  Schumacher, 
who  also  observed  all  manner  of  transition  forms  between  lymph  and 
hemolymph  nodes  as  far  as  the  relations  of  the  lymphatics  are  concerned, 
regarded  the  latter  as  rudimentary  or  undeveloped  lymph  nodes,  and  hence 
consistently  pronounced  against  their  being  organs  sui  generis,  v  Schu- 
macher distinguished  only  two  kinds  of  lymph  nodes,  viz.  (i)  those  with, 
and  (2)  those  without  lymph  vessels,  both  of  which  classes  may  contain 
erythrocytes  in  the  sinuses  and  parenchyma,  and  believed  in  a  transform- 


CLASSIFICATION  59 

ation  of  group  I  into  group  2,  and  also  regarded  a  retrans formation  prob- 
able. 

Baum  [  i  ]  recognized  two  classes  of  hemolymph  nodes :  those  with- 
out lymphatics,  which  he  designated  lymphoid  hemal  nodes;  and  those 
with  afferent  and  efferent  lymphatics,  or  lymphatic  hemal  nodes. 

Weidenreich  was  the  first  to  demonstrate  experimentally  that  the  so- 
called  hemolymph  nodes  in  the  sheep  are  wholly  independent  of  the  lym- 
phatic system,  thus,  in  a  measure,  justifying  Drummond's  supposition  that 
they  are  organs  sui  generis.  This  statement  of  Weidenreich  has  been 
abundantly  confirmed  by  the  present  investigation.  Consequently  there 
would  seem  to  be  no  need  for  any  more  than  two  classes  of  lymphoid 
organs — lymph  and  hemal  nodes.  That  not  all  hemal  nodes  varying  in 
structure  quantitatively  can  or  should  be  classified  separately  is  evident,  of 
course;  and  such  an  elaborate  classification  as  suggested  by  Lewis  [13] 
and  Warthin  [32  and  35]  is  unwarranted,  confusing,  and  certainly  un- 
scientific. The  many  structural  variations  in  hemal  nodes  to  which  atten- 
tion has  been  directed,  no  more  justify  separate  classification  than  would 
the  manifold  variations  in  external  form  of  such  an  organ  as  the  liver,  for 
example. 

Neither  the  term  hemal  nor  hemolymph  node  is  wholly  satisfactory  or 
an  appropriate  one,  however,  for  not  all  hemal  nodes  have  an  appreciable 
quantity  of  blood  in  the  parenchyma ;  although  they  are  intercalated  in 
the  vascular,  and  not  merely  in  the  venous  system,  as  has  been  variously 
stated.  Lymph  nodes,  on  the  contrary,  are  of  course  not,  as  the  term 
would  imply,  only  in  relation  with  the  lymphatic  system.  Hence  lymph 
nodes  are  virtually  the  only  true  hemolymph  nodes,  for  they  alone  have 
both  lymphatic  and  vascular  circulations  wholly  independent  of  each  other. 
The  term  hemoadenoid  would  be  clumsy  and  equally  confusing  as  hemo- 
lymph ;  and  while  the  term  splenic  is  undoubtedly  the  most  preferable  and 
proper,  in  spite  of  the  absence  of  Malpighian  corpuscles  in  almost  all 
hemal  nodes  of  the  sheep,  the  writer  does  not  feel  justified  in  introduc- 
ing another  term  and  thus  adding  to  the  confusion  which  already 
exists.  Hence  the  retention  of  the  term  hemal  node  seemed  commend- 
able. 

A  subdivision  of  hemal  nodes  into  active  and  inactive,  while  empha- 
sizing certain  prominent  physiological  differences,  would  not  be  exclusive 
either,  for  there  probably  are  very  few  nodes  in  which  functional  processes 
are  wholly  in  abeyance,  even  when  the  nodes  are  being  rapidly  depleted 
of  lymphocytes  and  converted  into  a  sac  of  blood.  Moreover,  we  know 
but  little  regarding  their  origin,  function  and  final  fate.  It  is  evident, 
of  course,  that  in  the  case  of  depleted  nodes,  poliferation  may  nevertheless 


60  HEMOLYMPH    NODES    OF    THE    SHEEP 

be  exceedingly  active,  even  while  the  node  is  depleted  rapidly.  Hence 
such  a  node  might  really  be  in  a  state  of  regeneration  and  of  hyperactivity, 
while  appearing  exhausted  and  depleted  and  hence  inactive.  But  the 
most  obvious  objection  to  a  physiological  classification  of  hemal  nodes  lies 
in  the  fact  that  all  manner  of  structurally  transitional  forms — i.  e.,  active 
and  inactive — occur  if  a  microscopical  examination  of  uninjected  speci- 
mens is  to  form  the  criterion.  Hence  in  the  present  state  of  our  knowl- 
edge— or,  better,  ignorance — all  attempts  to  subdivide  hemal  nodes  into 
a  number  of  definite  classes  must,  it  seems,  remain  entirely  futile  and 
wholly  unjustifiable  from  all  standpoints,  even  if  some  time  ago  both 
Lewis  and  Warthin  stated  that  certain  classes  of  hemal  glands  were  lim- 
ited to  certain  species. 

FUNCTIONS 

Clarkson,  working  on  the  horse,  sheep  and  pig ;  and  some  of  the  ear- 
liest observers,  and  very  recently  also  Meek  [17],  working  on  the  pig, 
thought  that  hemal  nodes  were  the  seat  of  formation  of  erythrocytes  as 
well  as  of  leucocytes.  Robertson,  e.  g.,  strangely  enough,  thought  that 
the  nuclei  of  the  large  multi-nucleated  leucocytes  became  erythrocytes; 
while  Meek,  writing  about  conditions  found  in  the  hemal  nodes  of  the  pig, 
says:  "Of  special  interest  are  certain  small  islets  of  cells  which  occur  in 
the  midst  of  the  blood  in  the  sinuses.  They  are  sharply  defined  from 
the  surrounding  red  blood  corpuscles,  and  are  formed  from  aggregations 
of  various  types  of  blood  cells.  One  such  focus  will  contain,  perhaps, 
fifty  closely-packed  normoblasts,  another  a  clump  of  myelocytes,  neutro- 
phylic  in  granulation,  while  yet  others  are  made  up  of  aggregations  of 
polymorphonuclear  cells.  Mitotic  figures  may  be  seen  in  the  cells  of  these 
islets."  .  .  .  "The  above  appearances  would  seem  to  suggest  that  a 
part  at  least  of  the  function  of  these  glands  in  the  pig  is  concerned  with 
the  formation  of  blood  cells,  red  and  white ;  and  they  are  described  at 
some  length,  as  they  differ  materially  from  the  conditions  found  in  any 
human  hemolymph  glands  examined."  These  observations  of  Meek  are 
unique,  for,  as  emphasized  by  Drummond  [5],  the  stages  in  the  formation 
of  erythrocytes  had  not  been  observed  in  developing  nodes  even.  How- 
ever, Drummond  too  believed  that  hemal  nodes  exercised  some  function 
in  connection  with  erythrocytes,  and  suggested  that  this  function  might 
be  a  cyclical  one.  This  conclusion  of  Drummond  was  based  on  the  great 
variability  in  cellular  content ;  which  variations,  within  the  same  or  dif- 
ferent species,  he  believed  to  be  due  to  varying  rates  of  blood  cell  destruc- 
tion. Drummond  further  thought  that  the  rate  of  destruction  of  erythro- 
cytes within  the  individual  node  or  species,  was  dependent  upon  the  num- 


FUNCTIONS  6l 

her  of  such  nodes  present.  Warthin  [33],  who  held  that  the  formation 
of  erythrocytes  undoubtedly  occurred  in  disease,  also  suggested  a  cyclical 
activity,  and  added  that  "the  appearances  (in  disease  in  man)  often  sug- 
gest a  transformation  of  adipose  tissue  into  lymphoid  tissue,  and  the  pos- 
sibility of  a  physiological  rotation  of  the  two  forms  of  tissue."  v  Schu- 
macher thought  it  possible  that  individual  erythrocytes  are  formed  in  the 
sheep,  but  regarded  such  an  origin  as  a  very  subsidiary  one.  He  found 
phagocytosis  by  reticulum  cells  and  a  fragmentation  of  erythrocytes  in 
the  phagocytes  in  some  nodes,  but  saw  few  pigment  cells.  An  extracellu- 
lar fragmentation  or  degeneration  of  erythrocytes,  as  observed  by  Weid- 
enreich,  is  denied  by  v  Schumacher, — a  denial  wholly  at  variance  with 
my  own  observations.  , 

That  the  destruction  of  erythrocytes — both  by  extra-  and  intra- 
cellular  disintegration  and  hemolysis — and  the  formation  of  leucocytes, 
occur  within  hemal  nodes,  is  undoubted.  That  these  processes  vary  extra- 
ordinarily in  degree  within  different  nodes  of  the  same  individual  and 
species,  as  well  as  in  those  of  different  species,  is  also  evident ;  and  while 
I  fully  realize  that  it  is  rather  venturesome  and  often  quite  futile  to  draw 
conclusions  regarding  function  from  a  purely  morphological  basis,  yet  it 
seems  to  me  that  the  supposed  function  of  "blood  destruction"  has  been 
wholly  over-emphasized.  Moreover,  it  might  pertinently  be  suggested 
that  it  is,  after  all,  not  "blood  destruction,"  but  mainly  destruction  of 
erythrocytes,  which  is  apparently  so  prominent  a  characteristic  of  some 
hemal  nodes.  Nevertheless,  since  so  many  hemal  nodes  contain  so  very 
little  blood,  even  when  practically  entirely  depleted  of  lymphatic  tissue, 
it  is  highly  improbable  that  destruction  of  erythrocytes  is  the  chief  or 
even  as  important  a  function  of  hemal  nodes  as  would  seem  to  be  the  case 
upon  cursory  examination.  For  even  if  destruction  of  erythrocytes,  be  it 
by  phagocytosis  or  by  erythrolysis  associated  or  unassociated  by  cytor- 
rhexis,  is  the  chief  function  of  hemal  nodes,  it  is  evident,  of  course,  that 
these  processes  must  in  all  probability  be  due,  and  solely  due,  to  some 
activity  on  part  of  the  parenchyma  of  the  hemal  node.  Hence  even  if 
this  destruction  within  the  node  were  due  in  part  to  the  production  of 
some  lysin,  one  might  reasonably  expect  the  quantity  of  lymphatic  tissue 
to  be  considerable,  or  proliferation  of  lymphocytes  most  active,  in  nodes 
containing  comparatively  large  quantities  of  blood.  This  is,  however, 
not  the  case ;  for,  as  is  evident,  the  quantity  of  lymphatic  tissue  must  of 
necessity  vary  inversely  with  the  quantity  of  contained  blood,  and  it  is 
only  rarely  that  many  follicles  are  found  in  depleted  nodes  or  in  any  hemal 
node  which  contains  much  blood.  And  even  when  this  is  the  case  and  rapid 
proliferation  of  lymphocytes  occurs,  this  very  activity  would  then  defeat 


62  HEMOLYMPH    NODES    OF    THE    SHEEP 

the  main  object  for  which  these  nodes  are  supposed  to  exist — viz.,  blood 
destruction.  For  just  in  proportion  as  the  hemal  node  became  more  able 
to  destroy  blood,  less  of  the  latter  would  be  able  to  stay  in  the  node,  since 
the  more  lymphatic  tissue  there  is,  the  less  blood  can  be  accommodated  in 
the  parenchyma  of  the  node.  And  it  is,  of  course,  in  the  latter  and  not 
in  the  vascular  current  within  the  node,  that  the  destruction  of  erythro- 
cytes  is  believed  to  occur.  Then,  too,  it  is  probable  that  the  volume  of 
flow  through  the  node  increases,  up  to  a  certain  point  at  least,  when  the 
node  is  undergoing  depletion  as  a  result  of  loss  of  lymphocytes  by  the 
blood  stream,  and  undoubtedly  also  as  a  consequence  of  the  exercise  of 
the  supposedly  specific  functions  of  the  node  in  this  connection.  Conse- 
quently, the  more  rapid  the  flow  and  the  larger  the  quantity  of  blood  that 
can  tarry  within  the  node,  the  smaller  the  power  of  the  node  will  be  to 
perform  the  very  task  for  which  it  is  supposed  to  exist.  That  is,  just  in 
proportion  as  the  need  for  the  exercise  of  their  function  of  blood  destruc- 
tion increased,  the  nodes  necessarily  would  become  progressively  less  com- 
petent to  fulfill  it.  Hence  rapid  self-destruction  would  seem  to  be  the  nec- 
essary result  of  the  exercise  of  a  supposedly  normal  physiological  activity. 
To  be  sure,  this  is  the  ultimate  fate  of  every  organ  and  organism ;  but 
it  seems  unlikely  that  organs  which  apparently  function  for  comparatively 
long  periods  of  time,  should  be  subjected  to  such  rapid  self-destruction 
when  the  need  for  their  activity  becomes  greater.  Since,  moreover,  the 
quantity  of  blood  in  some  hemal  nodes  is  so  very  insignificant,  and  since 
it  is  such  an  exceedingly  variable  one,  and  particularly  since  no  signs 
whatever  of  destruction  of  erythrocytes  can  be  noticed  in  many  nodes, 
it  is  difficult  indeed  to  regard  such  a  function  as  the  only  or  chief  role 
that  hemal  nodes  play  in  the  economy  of  the  organism.  Hence  for  this 
and  other  more  important  reasons,  the  designation  "hemolytic  organs," 
suggested  by  Warthin,  does  not  seem  to  be  justified ;  and  in  view  of  the 
above  facts  it  seems  more  probable  to  me  that  the  formation  of  leucocytes 
of  various  types,  rather  than  destruction  of  erythrocytes,  is  the  chief  func- 
tion of  the  hemal  nodes.  That  eosinophiles  are  formed  in  hemal  nodes 
one  can  scarcely  doubt,  and  the  same  is  true  of  phagocytes.  The  largest 
of  the  latter,  the  polykaryocytes,  and  some  megakaryocytes,  could,  to  be 
sure,  not  easily  leave  the  node  because  of  their  size,  and  probably  seldom 
do  so.  Since  these  poly-  and  megakaryocytes,  especially  those  of  giant 
size,  are  so  few,  however,  their  activity,  whatever  it  may  be,  is  probably 
not  a  very  important  one,  or  at  least  not  a  very  pronounced  one. 

The  supposition  that  formative  rather  than  destructive  processes  pre- 
vail in  hemal  nodes  also  receives  some  support  from  the  observations  of 


FUNCTIONS  63 

Warthin  [35]  and  others  to  the  effect  that  the  hemal  nodes — if  such 
there  be — of  man  are  enlarged  in  disease,  in  which  blood  destruction  is 
known  to  occur.  Moreover,  no  one  has  regarded  the  cause  of  the  blood 
destruction  to  lie  in  the  enlargement  of  these  nodes ;  and  it  would  seem 
more  probable  that  hyperactivity  in  them  at  such  a  time  should,  as  in  the 
case  of  the  bone  marrow,  be  regarded  as  a  constructive  rather  than  as  a 
primarily  destructive  reaction  or  process.  Then,  of  course,  there  is  the 
possibility  that  hemal  nodes  have  the  same  function  as  the  spleen — and 
supernumerary  spleens — whatever  that  may  be. 

Although  certain  aspects  of  the  cellular  content  and  a  discussion  of 
the  development  of  hemal  nodes  have  been  reserved  for  a  separate  art- 
icle, I  am  prompted  to  call  attention  to  certain  difficulties  confronting 
those  who  conclude  that  hemal  nodes  are  only  modified  lymph  nodes 
which  may  again  become  such  and  hence  cease  to  exist.  From  a  compar- 
ative anatomical  standpoint  it  would  seem  strange  that  this  accident  in 
development  is  restricted  not  only  to  certain  species,  and  predominates  in 
certain  regions  of  a  given  species,  but  occurs  so  much  more  frequently 
in  some  individuals — or  at  some  ages — of  a  given  species.  Moreover, 
since  the  panicular  and  subcutaneous  nodes  in  certain  regions  in  bovines, 
are  always  hemal  and  never  lymphatic  nodes,  and  since  the  largest  reg- 
ional lymph  nodes  are  never  converted  into  hemal  nodes,  the  problem  is 
complicated  still  further.  Besides,  up  to  the  present  it  has  not  been  shown 
that  true  hemal  nodes  in  bovines  and  sheep  become  diseased  when  the 
lymph  nodes  do ;  and  no  one  has  found  a  single  carcass  in  which  the  place 
occupied  so  frequently  by  scores  of  hemal  nodes  was  taken  by  a  corres- 
ponding number  of  somewhat  unusually  placed  lymph  nodes.  The  latter 
is  a  particularly  pertinent  consideration  in  view  of  v  Schumacher's  con- 
clusions and  statement  that  hemal  nodes  without  lymphatics  are  usually 
small ;  but  that  the  larger  hemal  nodes  usually  possess  lymphatics.  More- 
over, since  v  Schumacher  explicitly  stated  that  there  are  only  two  kinds 
of  lymph  nodes — those  with,  and  those  without  lymphatics — he  evidently 
uses  the  terms  hemolymph  node  (Blutlymphdrusen)  and  lymph  node 
synonymously.  From  embryological  evidence  in  my  hands  since  half  a 
decade,  it  is  also  clear  that  hemal  nodes  are  not  in  connection  with  the 
lymphatics  in  their  early  development,  and  that  lymph  sinuses  do  not  form 
in  them  at  this  time.  Furthermore,  from  the  numerous  observations  on 
the  carcasses  of  sheep  of  all  ages,  of  several  scores  of  the  new-born  of 
many  foetuses,  it  is  evident  that  it  is  absolutely  impossible  to  demonstrate 
the  pre-natal  or  early  post-natal  presence  of  a  comparable  number  of 
Anlagen  of  hemal  nodes  in  the  lumbar  sub-vertebral  region.  This  dif- 


64  HEMOLYMPH    NODES    OF    THE    SHEEP 

ficulty  is  apparently  met  by  v  Schumacher's  suggestion  that  lymph  nodes 
— among  which  he  includes  hemolymph  nodes — probably  continue  to  form 
in  post-natal  life. 

Then  there  are,  of  course,  the  structural  difficulties,  especially  those 
concerning  the  venous  system,  and  the  distribution  and  character  of  the 
so-called  blood  sinuses  of  hemal  nodes,  said  to  correspond  to  those  of 
lymph  nodes,  which  must  be  met  by  those  who  maintain  a  conversion  of 
one  type  of  node  into  the  other.  To  be  sure,  I  am  fully  aware  that  there 
are  also  difficulties  and  interrogations  to  be  met  by  those  who  have  been 
prompted  to  believe  in  the  morphological  identity  of  hemal  nodes.  The 
discussion  of  these  will  be  reserved  for  a  separate  article  on  the  hemal 
nodes  of  Bos  taurus  and  Capra  hircus. 


APPENDIX 


APPENDIX 

A  short  summary  of  other  articles  by  the  writer,  on  the  subject  of 
hemal  nodes  and  related  structures,  is  appended  for  the  convenience  of 
those  who  may  not  have  access  to  all  of  them. 

I.  SUBCUTANEOUS  AND  SUB-PANICULAR  HAEMOLYMPH   GLANDS.     Ana- 

tomical Record,  vol.  II,  Nos.  i  and  2,  May  1908. 

Under  this  title  a  brief  statement  of  a  report  given  before  the  Asso- 
ciation of  American  Anatomists  in  Chicago,  in  December  1907,  was  pub- 
lished with  the  proceedings  of  the  society  in  the  Anatomical  Record,  vol. 

II,  nos.  i  and  2,  May  1908.     In  this  report  it  was  stated  that  while  en- 
gaged in  an  investigation  of  the  hemal  nodes  of  the  sheep  in  the  abat- 
toirs of  Minneapolis,  where  bovines  were  being  simultaneously  slaugh- 
tered, my  attention  was  directed  to  nodes  lying  in  the  subcutaneous  fat  of 
the  trunk  of  carcasses  of  bovines.    These  nodes  were  found  to  vary  in 
number,  from  isolated  specimens  to  approximately  a  score,  and  varied  in 
size  from  one-half  to  one  and  a  half  centimeters.   They  were  oval  or  cir- 
cular in  outline,  and  usually  flattened  laterally.  It  was  stated  that  "In  color 
they  vary  from  a  bluish  black  to  a  bright  red  or  pale  pink.     They  are 
usually  firm,  the  blood  cannot  be  expressed  from  them  by  pressure,  and 
injections  of  India  ink  fail  to  reveal  any  lymphatic  vessels.     They  are 
most  numerous  in  young  cattle,  and  were  found  in  foetuses  of  twenty- 
two  or  more  centimeters  in  length.     In  old  cattle  they  are  generally 
small  or  absent  altogether. 

"Their  structure  is  very  similar  to  that  of  the  haemolymph  nodes  of 
sheep,  and  as  wide  variations  in  structure  were  found  to  exist.  Such 
differences  in  structure  as  exist  are  minor,  even  in  the  case  of  develop- 
ing glands.  In  the  latter  the  occurrence  of  giant  cells  is  particularly 
noticeable,  and,  as  in  the  case  of  developing  haemolymph  nodes  of  the 
sheep,  they  arise  from  mesenchyme. 

"In  carcasses  showing  evidences  of  generalized  tuberculosis,  no 
change  in  these  nodes  was  noticeable. 

"No  relation  between  the  size  and  number  of  these  nodes  and  any 
condition,  save  that  of  age,  was  observed,  although  such  a  relationship 
very  likely  exists." 


66  HEMOLYMPH    NODES    OF    THE    SHEEP 

II.  THE  HAEMOLYMPH  GLANDS  OF  THE  SHEEP.    Ibid. 

In  this  report,  among  other  things  it  was  stated  that  the  earliest  dif- 
ferentiation between  the  Anlagen  of  lymph  and  hemal  nodes  was  observed 
in  foetuses  9.8  cm.  long,  and  that  hundreds  of  injections  from  adjacent 
nodes,  from  the  surrounding  tissues  as  well  as  others  made  from  the  aorta 
and  vena  cava  and  from  large  lymph  vessels  and  nodes,  proved  conclus- 
ively that  the  hemolymph  nodes  of  the  sheep  are  independent  of  the 
lymphatic  system  and  are  not  intercalated  in  the  veins.  The  following 
were  some  of  the  other  conclusions  stated  there: 

1.  That  the  reticulum  is  not  lined  by  endothelium. 

2.  That  the  circulation  is  an  open  one. 

3.  That  the  peripheral  sinus  and  blood  sinuses  are  not  in  direct  con- 
nection with  either  the  venous  lacunae  of  Weidenreich  or  with  the  arteries, 
save  developmentally. 

4.  That  the  peripheral  sinus  and  blood  sinuses  are  inconstant  struct- 
ures, while  the  venous  lacunae  are  always  present,  even  if  not  evident, 
on  cross-section  of  a  node. 

5.  That  the  arteries  communicate  with  the  venous  lacunae,  and  that 
the  latter  communicate  with  each  other  and  with  the  veins. 

6.  That  the  relation  of  the  vein  or  veins  to  the  node  is  an  exceedingly 
variable  one,  and  is  frequently  merely  a  contact  relationship. 

7.  That  small   veins   occasionally  join   the   haemolymph   nodes   by 
penetrating  the  capsule  near  the  periphery,  and  that  these  veins  are  af- 
ferent veins. 

8.  That  it  is  easy  to  distinguish  a  haemolymph  node  from  a  lymph 
node  by  means  of  injection,  and  that  it  is  equally  easy  to  distinguish  a 
venous  injection  from  an  arterial  one. 

9.  That  pigment  is   rarely  found  in  haemolymph  nodes,  but  fre- 
quently in  lymph  nodes. 

10.  That  "mixed  glands,"  i.  e.,  true  haemolymph  glands,  were  not 
found. 

11.  That  the  haemolymph  nodes  of  the  sheep,  goat,  and  bovines  are 
very  similar  in  structure. 

12.  That,  in  view  of  these  facts,  the  word  haemolymph  as  applied  to 
these  nodes  in  the  sheep  is  a  misnomer,  and  that  the  term  haemal  node, 
suggested  by  Lewis,  is  to  be  preferred. 


APPENDIX  C>7 

III.  THE  EXPERIMENTAL  PRODUCTION  OF  HEMOLYMPH  NODES  AND  AC- 

CESSORY SPLEENS.  Journal  of  Experimental  Zoology,  vol.  16,  1914. 
After  a  critical  review  of  the  literature  on  the  above  subject,  the  re- 
sults of  a  series  of  experiments  on  guinea-pigs  and  dogs  are  recorded 
and  discussed.  No  hemal  nodes  or  accessory  spleens  were  formed  as  re- 
sult of  splenectomy  in  young  dogs,  and  no  hemal  nodes  or  reddened 
lymph  nodes  were  produced  in  guinea-pigs  by  the  repeated  injection  of 
toxine  and  other  substances,  or  by  a  hundred  or  more  successive  with- 
drawals of  blood  in  the  sheep;  but  that  changes  may  be  produced  in 
lymph  nodes  by  repeated  bleeding  is  suggested  by  the  studies  of  Smith, 
indicating  a  lowering  of  the  resistance  of  erythrocytes  after  the  with- 
drawal of  blood.  However,  it  is  more  than  likely  that  the  amount  and 
frequency  of  that  loss  are  very  important  factors  in  the  determination  of 
the  character  and  extent  of  the  changes  in  lymph  nodes;  a  conclusion 
which  would  also  seem  to  be  amply  justified  by  Freytag's  observations. 

IV.  HEMAL  NODES  IN  SOME  CARNIVORA  AND  RODENTS.     Anatomischer 

Anzeiger,  Bd.  45,  1913. 

An  examination  of  a  large  series  of  cats  and  dogs  of  all  ages  failed 
to  reveal  any  hemal  nodes,  other  than  supernumerary  spleens,  in  these 
animals.  Similar  conclusions  were  also  reached  regarding  mice,  rats, 
guinea-pigs  and  rabbits,  but  as  a  result  of  an  examination  of  a  much  small- 
er number  of  animals.  The  structural  relation  of  supernumerary  spleens 
and  hemal  nodes  is  also  considered  briefly,  and  the  occurrence  of  mixed 
lymph  and  hemal  nodes  referred  to.  The  retrogression  of  blood  and 
chyle  in  the  larger  lymph  vessels  of  the  dog  is  reported,  and  its  signific- 
ance in  the  production  of  mixed  nodes  emphasized. 

Errata  in  this  article  as  published  in  the  Anat.  Anz.:  HEMAL  NODES  IN 
SOME  CARNIVORA  AND  RODENTS.  STUDIES  ON  HEMAL  NODES,  III.  Anat. 
Anz.,  No.  12,  Bd.  45,  1913. 

P.  261,  line  8— Delete  the  period. 

P.  263,  footnote  reference  (2) — Read  Meyer,  Anat.  Rec.,  Phila., 
1914,  instead  of  1913. 

P.  263,  line  4 — Read  obtained,  instead  of  contained. 

P.  268,  footnote  reference  (i) — Read  Meyer,  The  Hemolymph 
Nodes  of  the  Sheep.  Studies  on  Hemal  Nodes,  I.  University  Publica- 
tion, Stanford  University. 

P.  269,  line  3 — Read  these  species. 

P.  271,  reference  34 — Line  2,  add  der  Milz  to  the  title. 


68  HEMOLYMPH    NODES    OF    THE    SHEEP 

V.  THE  OCCURRENCE  OF  SUPERNUMERARY  SPLEENS  IN  DOGS  AND  CATS, 

WITH  OBSERVATIONS  ON  CORPORA  LIBERA  ABDOMINALIS.     Ana- 
tomical Record,  vol.  8,  1914. 

In  view  of  the  experiments  of  Tizzoni  and  other  investigators  of  that 
period,  and  also  for  other  reasons,  it  became  necessary  to  possess  reliable 
data  regarding  the  occurrence  of  accessory  spleens  in  dogs  and  cats,  in 
connection  with  investigations  on  hemal  nodes  in  the  domestic  animals. 
A  series  of  careful  examinations  on  67  dogs  and  82  cats  of  all  ages  showed 
that  supernumerary  spleens  are  present  in  14.6  per  cent  of  the  cats,  and 
that  the  number  in  a  single  animal  may  vary  from  one  to  approximately 
five  hundred.  The  existence  of  peculiar  pedunculated  omental  appen- 
dages— literally  appendices  epiploicae — was  also  reported,  and  the  re- 
lation of  these  to  the  occurrence  of  corpora  libera  abdominalis  discussed. 
Similarly  8.9  per  cent  of  the  dogs  had  supernumerary  spleens,  the  num- 
ber per  animal  varying  from  one  to  over  eight  hundred.  The  bearing 
of  these  facts  on  the  results  of  the  older  experiments  and  on  the  occur- 
rence of  hemal  nodes  in  these  animals,  is  discussed  critically.  Several 
plates  represent  cross-sections  and  gross  views  of  some  of  the  specimens. 

VI.  HEMAL  NODES  IN  Bos  taurus  AND  Capra  hircus.     (In  publication.) 
In  addition  to  a  description  of  the  hemal  nodes  of  goats  and  bovines, 

special  emphasis  is  placed  on  the  subcutaneous  and  subpanicular  nodes  of 
Bos  taurus,  and  on  the  development  of  the  latter  and  of  hemal  nodes  in 
general. 


REFERENCES 

1.  Baum:    Konnen    Lymphgefasse    direkt    in    Venen    einmiinden? 
Anat.  Anz,,  Bd.  39,  1911. 

ia.     Baum:  Rote  Lymphknoten.     Deutsch.   Tierarzt.   Wochenschr., 
1907. 

2.  Clarkson,  Arthur:    Report  on  haemal  glands.     Brit.  Med.  Jr., 
vol.  2,  July  25,  1891. 

3.  Clarkson,  Arthur:  A  text-book  on  Histology.     Saunders,  Phil., 
1896. 

4.  Dayton,    Hughes :     Haemolymph    nodes.     Am.   Jr.    Med.    Sci., 
vol.  131,  1904. 

5.  Drummond,  W.   B. :    On  the  structure  and  function  of  hemo- 
lymph  glands.     Jr.  Anat.  and  Phys.,  Lond.,  vol.  34,  1900. 

6.  Forgeot:    Sur  quelques  particularites  des  ganglions  hemolym- 
phatiques  des  ruminants.     Comptes  Rendus,  Assoc.  Anat.,  Nancy,  1909. 
Accessible  in  review  only. 

7.  Forgeot:     Sur   quelques    dispositions   des   ganglions   hemolym- 
phatiques  des  ruminants.     Assoc.  Franchise  pour  1'avancement  des  Sci- 
ences, 376  session.     Clermont-Ferrand,  1908.     Accessible  in  review  only. 

8.  Gibbes,  H. :    On  some  structures  found  in  the  connective  tissue 
between  the  renal  artery  and  vein  in  the  human  subject.     Quar.  Jr.  of 
Microscop.  Sci.,  Lond.,  vol.  24,  1883. 

9.  Gibbes,  H. :    Hemolymph  glands.     Am.  Jr.  Med.  Sci.,  vol.  106 
(n.s.),  1893. 

10.  Haberer:    Lien  succenturiatus  und  lien  accessorius.     Arch.  f. 
Anat.  u.  Phys.  Anat.,  Abt.  1901. 

11.  Helly,   Konrad:   Haemolymphdriisen.     Ergeben.  der  Anat.   u. 
Entwicklgsch.,  Bd.  12,  1912. 

1 1  a.     Huntington:    Ueber  die  Histogenese  des  lymphtischen  Sys- 
tems beim  Saugerembryo.     Anat.  Anz.,  Erganzhft.,  Bd.  37,  1910. 

12.  Lewis,  Thomas:    The  structure  and   function  of  the  haemo- 
lymph  glands  and  spleen.     Internat.  Monatschrift.  f.  Anat.  u.  Phys.,  Bd. 
20,  1902. 

13.  Lewis,  Thomas:  Observations  upon  the  distribution  and  struc- 
ture of  hemolymph  glands  in  mammalia  and  aves,  including  a  prelimi- 
nary note  on  the  thymus.     Jr.  Anat.  and  Phys.,  Lond.,  vol.  38,  1904. 

14.  Lewis,  Thomas:    Further  observations  on  the  functions  of  the 
spleen  and  other  haemolymph  glands.     Ibid. 

15.  McCarthy,  D.  J. :    The  formation  of  haemolymph  glands  from 
adipose  tissue  in  man.     Jr.  Med.  Research,  Boston,  vol.  9,  1903. 


70  HEMOLYMPH    NODES    OF    THE    SHEEP 

16.  McClure  and  Silvester:   A  comparative  study  of  the  lymphatic- 
venous   communications   in  adult   mammals.      Ant.   Record,   Phil.,   vol. 
3,  1909. 

17.  Meek,  Q.  O. :    Some  morbid  histological  changes  met  with  in 
the   lymphatic   glands,   especially   in   connection   with   the    formation   of 
haemolymph  glands.     Quarterly  Jr.  Med.,  Oxford,  vol.  3,  1910. 

1 8.  Morandi  and  Sisto:    Contribution  a  1'etude  des  glandes  hemo- 
lymphatiques  chez  1'homme  et  chez  quelques  mammiferes.     Arch.  ital.  de 
Biol,  vol.  35,  1901. 

19.  Retterer:    Origine  du  plasma  et  de  la  lymph  et  hematics  lym- 
phatiques.     Jr.  de  I'Anat.,  T.  46,  1910. 

20.  Retterer:    Sur  les  circonstances   dans  laquelles  on  obtient  la 
disparition  des  hematies  des  ganglions  lymphatiques  ou  leur  stase  dans 
les  sinus  de  1'organe  (gland  hemolymphatique).     Comptes  Rendus,  vol. 
54,  1902. 

21.  Retterer:   Sur  les  modifications  que  determine  1'abstinence  dans 
les  ganglions  lymphatiques.     Ibid. 

22.  Retterer:    Structure   et   fonction   des   ganglions   lymphatiques 
dans  1'espece  humaine.     Ibid. 

23.  Retterer  et  Lelievre:    Precede  simple  pour  voir  que  le  ganglion 
lymphatique  possede  des  hematics.     Comptes  Rendus  Soc.  Biol.,  T.  68, 
1910. 

24.  Robertson,   W.    F. :    The    prevertebral    haemolymph    glands. 
Lancet,  vol.  2,  Nov.  29,  1890. 

25.  Saltykow :     Uber    bluthaltige    Lymphdriisen    beim    Menschen. 
Zeitschr.  f.  Heilk.,  1900. 

26.  Silvester:    On  the  presence  of  permanent  communications  be- 
tween the  lymphatic  and  venous  systems  at  the  level  of  the  renal  veins  in 
adult  South  American  monkeys.     Am.  Jr.  Anat.,  vol.  12,  1911. 

27.  v  Schumacher:    Bau,  Entwicklung  und  systematische  Stellung 
der  Blutlymphdriisen.     Archiv  f.  mikr.  Anat.,  Bd.  8l,  1912. 

270.     v  Schumacher:    Ueber  Blutlymphdriisen.     Verhandl.  deutsch. 
Anat.  Gesell.     Anat.  Anz.,  Erganzhft.  41,  1912. 

28.  Vincent  and  Harrison  :   On  the  hemolymph  glands  of  some  ver- 
tebrates.    Jr.  Anat.  and  Phys.,  Lond.,  vol.  31,  Jan.  1897. 

29.  Vincent,  S :   On  haemolymph  and  haemal  lymphatic  glands.  Jr. 
Phys.,  Lond.,  vol.  22,  1898;  Proc.  Physiol.  Soc.,  p.  XL. 

30.  Vincent,  S. :   The  hemolymph  glands  of  some  vertebrates.    Jr~ 
Anat.  and  Phys.,  Lond.,  vol.  31,  1896-97. 

31.  Warthin,  A.  S. :  The  normal  histology  of  the  human  hemolymph 
glands.     Am.  Jr.  Anat.,  vol.  i,  1901. 

32.  Warthin,  A.   S. :    The  pathology  of  pernicious  anemia,   with 
special  reference  to  changes  occurring  in  hemolymph  nodes.     Amer.  Jr. 
Med.  Sci.,  vol.  124,  1902. 


REFERENCES  71 

33.  Warthin,  A.  S. :    A  contribution  to  the  normal  histology  and 
pathology  of  the  hemolymph  glands.     Jr.  Boston  Soc.  Med.  Sci.,  vol.  5, 
1901. 

34.  Warthin,  A.  S. :  The    changes    produced    in    the    hemolymph 
glands  of  the  sheep  and  goat  by  splenectomy,  hemolytic  poisons  and  hem- 
orrhage.    Jr.  Med.  Research,  vol.  7  (n.  s.),  July,  1902. 

35.  Warthin,  A.  S  :  Are  the  haemolymph  nodes  organs  sui  generis? 
Trans.  Chicago  Path.  Soc.,  vol.  5,  1902. 

36.  Warthin,  A.  S. :    Pseudomelanosis  of  the  haemolymph  glands. 
Am.  Jr.  Med.  Sci.,  vol.  128  (n.  s.),  1904. 

37.  Weidenreich,  F. :    Studien  iiber  das  Blut  und  die  blutbildenden 
und  zerstorenden  Organe.     Arch.  f.  Mikr.  Anat.,  Bd.  65,  1904. 

38.  Weidenreich,  F. :  Ueber    Blutlymphdriisen.     Anat.  Anz.,  vol. 
20,  1901. 

39.  White :  Hemolymph  glands  in  domestic  animals.    Am.  Jr.  Anat., 
vol.  3,  1904;  Proc.  Ass.  Am.  Anat.,  p.  VIII. 


DESCRIPTION  OF  PLATES 

FIG.  i.— A  small  (5  mm.)  oval  hemal  node  supplied  with  two  parallel  veins 
whose  contour  suggests  lymphatics.  These  veins  gave  off  two  branches,  as  indi- 
cated, and  joined  to  form  a  single  trunk  of  the  usual  appearance. 

FIG.  2. — A  node  similar  to  that  represented  in  fig.  i,  with  adjacent  smaller 
nodes  with  veins  of  similar  character. 

FIG.  3. — A  group  of  small  discrete  hemal  nodes  simulating  a  long,  tortuous  sin- 
gle node. 

FIG.  4. — Appearance  of  the  group  of  nodes  shown  in  fig.  3  as  seen  in  longi- 
tudinal section.  Right  half. 

FIG.  5. — Hemal  node  injected  with  India  ink  from  the  vein  by  puncture  from 
an  adjacent  node.  This  node  contained  many  exceedingly  large  phagocytes  shown 
as  red  dots  all  over  the  section,  even  in  the  follicles.  All  the  ink  lies  in  the  venous 
radicles  in  the  parenchyma. 

FIG.  6. — Section  of  another  node  injected  similarly  to  the  one  in  fig.  5.  Some 
pigment  is  free  in  the  parenchyma  and  in  the  follicles,  but  very  little  is  found  in 
the  hemal  areas. 

FIG.  7. — Hemal  node  adjacent  to  the  thymus  from  a  lamb  4-5  months  old.  In- 
jected with  carmine  gelatine  from  the  abdominal  aorta.  The  injection  is  only  a 
partial  one,  because  the  aorta  was  ligated  proximally  to  the  point  of  injection. 

FIG.  8. — Camera  lucida  drawing  of  a  small  hemal  node  from  a  goat.  The  trib- 
utary veins  are  shown  in  section  at  the  bottom  and  to  the  right,  where  they  commu- 
nicate directly  with  the  peripheral  venous  lacunae  but  not  with  the  subcapsular  blood 
space.  The  lacunae — true  venous  sinuses — which  are  continuous,  are  bounded  by 
an  endothelial  wall,  and  successive  sections  illustrate  the  relation  of  the  veins  to 
them  and  to  the  subcapsular  blood  space  very  clearly. 

FIG.  9. — An  injected  lymph  node  from  a  lamb,  showing  the  wholly  different  char- 
acter of  the  injection  as  compared  with  those  in  figs.  5  and  6. 

FIG.  10. — A  hemal  node  from  a  goat,  showing  a  vein  and  an  artery  which  pass 
entirely  through  the  node.  Although  the  vein  comes  in  contact  with  the  hemal 
areas,  it  opens  only  into  the  parenchyma.  Note  the  absence  of  a  hilus,  relation  of 
the  venous  lacunae — clear  spaces — to  the  hemal  areas,  and  the  relation  of  the  latter 
to  each  other.  Camera  lucida. 

FIG.  IT. — Another  section  of  the  same  node  showing  the  artery  in  longitudinal 
section  and  the  direct  continuation  of  the  subcapsular  blood  area  into  a  peri-arterial 
one.  Camera  lucida. 

FIG.  12. — Two  veins  tributary  to  the  subcapsular  blood  space  of  a  hemal  node 
from  the  sheep.  Camera  lucida. 

FIG.  13. — A  portion  of  a  node  injected  with  India  ink  from  an  adjacent  node. 
The  pigment  lies  in  the  lymphatic  tissue,  and  has  not  invaded  the  large  blood  space 
which  it  surrounds,  x  290. 

FIG.  14. — A  cross-section  of  a  node  largely  depleted  of  lymphatic  tissue,  and 
containing  very  many  follicles  and  numerous  large  veins. 

Note — Please  view  figures  6,  9  and  18  with  a  reading  glass. 


74  HEMOLYMPH    NODES    OF    THE    SHEEP 

FIG.  15. — A  node  in  which  the  hemal  area  is  large  and  continuous,  and  in  which 
the  remaining  lymphatic  tissue  is  found  chiefly  at  the  periphery. 

FIG.  16. — A  portion  of  an  almost  empty  node  in  which  all  the  venous  radicles 
or  lacunae  are  found  surrounded  by  lymphatic  tissue.  A  few  of  these  communicate 
directly  with  the  large  hemal  area,  which  contains  little  blood  and  many  fragments 
of  erythrocytes.  This  node  is  subdivided  more  or  less  completely  by  thick  con- 
nective tissue  septa. 

FIG.  17. — Camera  lucida  drawing  of  a  node  containing  but  little  lymphatic  tissue, 
at  the  periphery  of  which  a  large,  almost  continuous  lacuna  is  seen. 

FIG.  18. — A  section  of  an  almost  depleted  node,  showing  the  characteristic  dis- 
tribution of  the  lymphatic  tissue  with  the  contained  venous  lacunae. 

FIG.  19. — A  section  of  a  similar  node.  The  entire  absence  of  follicles  and  the 
profoundly  modified  architecture  suggest  that  such  nodes  are  disappearing. 

FIG.  20. — A  small  portion  of  a  hemal  node,  showing  a  venous  lacuna  opening 
directly  into  the  parenchyma  at  the  left,  where  the  degenerating  erythrocytes  and  a 
large  phagocyte  lie.  x  410. 

FIG.  21. — A  large  venous  lacuna  containing  granular  detritus  and  surrounded 
by  hemal  areas  composed  almost  wholly  of  excellently  preserved  erythrocytes, 
which  are  everywhere  separated  from  it  by  definite  walls  and  a  narrow  border  of 
lymphatic  tissue,  x  920. 

FIG.  22. — A  partially  collapsed  venous  lacuna,  showing  a  definite  endothelial 
wall  on  one  side  and  a  barrier  of  lymphatic  tissue  on  the  other,  separating  it  from 
the  surrounding  hemal  areas,  x  920. 

FIG.  23. — A  rare  section  showing  the  communication  of  a  capillary  with  a  venous 
lacuna,  x  750. 

FIG.  24. — A  section  through  a  process  of  lymphatic  tissue  containing  a  large 
hemal  area,  which  projects  into  a  large  venous  lacuna  or  sinus.  There  is  no  direct 
communication  between  the  latter  and  the  hemal  area  anywhere,  x  630. 

FIG.  25. — A  portion  of  a  large  hemal  area  containing  abundant  and  coarse  retic- 
ulum.  In  many  places  the  reticulum  fibers  have  no  doubt  been  forced  together. 
x  630. 

FIG.  26. — A  portion  of  a  node  showing  the  accumulation  of  eosinophiles  around 
the  artery.  Several  degenerating  giant  cells  are  also  seen,  x  1340.  p.  61. 

August  25,  1913. 


No.  6 


No.  1O 


No.  11 


No.  15 


No.  17 


NO.  2O 


No.  21 


No.  22 


No.  23 


No.  24 


No.  25 


No.  26 


THE  BIRDS  OF  THE  LATIN  POETS.     Ernest  Whitney  Martin,  Associate 

Professor  of  Greek.    260  pp.    1914.    Price,  $1.00. 
ACCELERATION    IN    THE    DEVELOPMENT   OF   THE  FOSSIL   CEPHALOPODA. 

James  Perrin  Smith,  Professor  of  Paleontology.    30  pp.,  15  plates. 

1914.    Price,  75c. 
A  MORPHOLOGICAL  STUDY  OF  SOME  MEMBERS  OF  THE  GENUS  PALLAVI- 

CINIA.    Douglas  Houghton  Campbell  and  Florence  Williams.    44 

pp.,  23  text  figures.     1914.    Price,  5oc. 
THE  EVOLUTION  OF  BRAZIL  COMPARED  WITH  THAT  OF  SPANISH  AND 

ANGLO-SAXON   AMERICA.     Manuel  de  Oliveira  Lima.      160  pp. 

1914.     Price,  $1.00. 
THE    HEMOLYMPH    NODES    OF   THE    SHEEP.    Arthur    William    Meyer. 

74  pp.,  i  plate,  4  colored  plates.     1914.     Price,  $1.00. 


Date  Due 


Demco  38-297 


QP91 

M5S 

191U 


Meyer,  Arthur  William 

The  hemolymph  nodes  of  the 
sheep. 


QP91 
M55 


Meyer,  Arthur  William 

The  hemolymph  nodes  of  the 
sheep. 


BID-AGRICULTURAL  LIBRARY 
UNIVERSITY  OF  CALIFORNIA 
RIVERSIDE.  CALIFORNIA  92502 


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